One-flask synthesis of mono- and trifunctionalized 21-thia and 21-oxaporphyrin building blocks and their application in the synthesis of covalent and noncovalent unsymmetrical porphyrin arrays

On e-F la sk Syn th esis of Mon o- a n d Tr ifu n ction a lized 21-Th ia a n d

21-Oxa p or p h yr in Bu ild in g Block s a n d Th eir Ap p lica tion in th e

Syn th esis of Cova len t a n d Non cova len t Un sym m etr ica l P or p h yr in

Ar r a ys^†

Iti Gupta and Mangalampalli Ravikanth*

Department of Chemistry, Indian Institute of Technology, Bomay, Powai, Mumbai 400 076, India

ravikanth@chem.iitb.ac.in

Received April 20, 2004

A rapid synthetic route has been developed to synthesize mono- and trifunctionalized 21-thia and

21-oxaporphyrin systems using simple precursors such as 2[R-(aryl)-R-hydroxymethyl] thiophene

(thiophene mono-ol) and 2[R-(aryl)-R-hydroxymethyl] furan (furan mono-ol), respectively. Condensa-

tion of one equivalent of thiophene or furan mono-ol with two equivalents of aryl aldehyde and

three equivalents of pyrrole under porphyrin forming conditions followed by column chromatography

resulted in functionalized 21-thia or 21-oxaporphyrins. To synthesize monofunctionalized porphyrins,

the mono-ol containing the functionalized aryl group was used. The functionalized aldehydes were

used to synthesize trifunctionalized porphyrins. The mono-ol method is versatile and applicable to

synthesize mono- and trifunctionalized 21-thia and 21-oxaporphyrins containing functional groups

such as iodophenyl, ethynylphenyl, hydroxyphenyl, bromophenyl, and pyridyl groups. The mono-

functionalized porphyrin building blocks containing iodophenyl and ethynylphenyl groups were

used further to synthesize four unsymmetrical covalent porphyrin dimers containing two different

porphyrin cores such as N₃S-N₄, N₃O-N₄, and N₃S-N₃O bridged via diaryl ethyne group and one

symmetrical phenylethyne bridged dimer containing two N₃S cores. A preliminary photophysical

study on these dimers indicated a possibility of energy transfer from one subunit to another. We

also demonstrated the use of trifunctionalized porphyrins in the synthesis of two noncovalent

unsymmetrical porphyrin tetramers containing one N₃S and three N₄porphyrin subunits.

In tr od u ction

subunits of porphyrin arrays, the 100% selective excita-

tion is not possible. The selective excitation of the

porphyrin unit to induce electron or energy transfer in a

particular direction can be achieved easily if the porphy-

rin units in the array are not identical (unsymmetrical).

In the recent past, attention has been directed toward

synthesizing covalently linked unsymmetrical arrays³

containing two different macrocycles such as a porphy-

rin-pyropheophorbide, porphyrin-chlorin, porphyrin-

corrole, or porphyrin-phthalocyanine to obtain fast

initial charge transfer and a slow back reaction, so giving

a long-lived charge-transfer state. A common feature

among the various unsymmetrical dimers reported so far

is that they all have similar pyrrole nitrogens as donor

atoms (N₄cores).

The covalent and noncovalent linking of porphyrins

and related macrocycles into dimers and larger arrays

has been exhaustively studied in recent years to under-

stand the energy and electron-transfer processes of

photosynthesis. Most synthetic models for photosynthesis

contain two covalently linked porphyrins which are

attached to each other by one or more bridging groups

such as phenyls, biphenyls, aromatic heterocycles, al-

kenes, or alkynes.¹Supramolecular assemblies held

together by noncovalent forces²such as hydrogen bonding

and metal-pyridyl interactions have also been synthe-

sized as model compounds for photosynthetic processes

in natural systems. However, most of these covalent and

noncovalent porphyrin arrays were symmetrical in na-

ture containing two identical macrocycles; hence, it was

difficult to achieve selective excitation of porphyrin unit

upon irradiation. The direction of photoinduced energy

or electron transfer has been generally induced in por-

phyrin arrays by selective metalation of the porphyrin

subunits. However, since the absorption bands of meta-

lated porphyrin overlaps with the free base porphyrin

One area of porphyrin chemistry that has received less

attention but may lead to systems of interesting struc-

tural and electronic properties is the characterization of

porphyrin dimers with dissimilar cores. One of the most

interesting modifications of the porphyrin molecule would

be the replacement of the core nitrogens by other het-

eroatoms such as sulfur, oxygen, selenium, tellurium, and

so forth.⁴Thus, a series of heteroatom substituted por-

phyrins form a group of core-modified porphyrins that

exhibit interesting properties in terms of both aromatic

^†This paper is dedicated to a porphyrin chemist the late Professor

Bhaskar G. Maiya (1956-2004).

Published on Web 09/04/2004

6796

J . Org. Chem. 2004, 69, 6796-6811

One-Flask Synthesis

SCHEME 1. Gen er a l Syn th etic Sch em e for 21-Th ia a n d 21-Oxa p or p h yr in s

character and their ability to stabilize metals in unusual

oxidation states.^4aAn assembly of such heteroatom

substituted porphyrin (N₃S, N₃O, N₂S₂, N₂O₂, N₂SO) and

normal porphyrin (N₄core) would offer unique dimers

and oligomers which are expected to have unusual

electronic structure and interesting properties. Recently,

Van Patten and co-workers⁵proposed that a set of

heteroatom porphyrins such as N₄, N₃O, N₃S, N₂OS, and

N₂S₂arranged in a linear series with a progressive

decrease in energy levels could provide the basis for an

energy cascade. There are very few examples of unsym-

metrical porphyrin dimers and oligomers containing

heteroatom substituted porphyrins available in the

literature.^6-8Since the heteroatom substituted porphyrin

building blocks with desired functional groups are very

rare in the literature because of limited synthetic meth-

ods available, the chemistry of porphyrin arrays contain-

ing heteroporphyrins is not very well developed.

phene or furan (thiophene diol or furan diol) with an

aldehyde and pyrrole under standard porphyrin reaction

conditions resulted in the formation of N₃S or N₃O

porphyrins. This method is useful to prepare 21-thia or

21-oxaporphyrins bearing only one type of meso-substitu-

ent or two types of meso-substituents in a cis configura-

tion. We explored this method extensively and synthe-

sized several heteroatom substituted porphyrins.¹⁰

(2) Some selected examples of noncovalently linked porphyrin

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Pandey, R. K.; Forsyth, T. P.; Gerzevske, K. R.; Lin, J . J .; Smith, K.

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1993, 34, 693. (f) Paolesse, R.; Pandey, R. K.; Forsyth, T. P.; J aquinod,

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T.; Smith, K. M. J . Am. Chem. Soc. 1996, 118, 3869. (g) Kadish, K.

M.; Guo, N.; Camelbecke, E. V.; Froiio, A.; Paolesse, R.; Monti, D.;

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Chem. 1998, 37, 2358. (h) Li, J .; Diers, J . R.; Seth, J .; Yang, S.-I.;

Bocian, D. F.; Holten, D.; Lindsey, J . S. J . Org. Chem. 1999, 64, 9090.

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drashekar, T. K. Struct. Bonding 1995, 82, 105 and references therein.

(5) Van patten, P. G.; Shreve, A. P.; Lindsey, J . S.; Donhoe, R. J . J .

Phys. Chem. B 1998, 102, 4209.

The general synthetic scheme used for synthesis of 21-

thia^9a,band 21-oxaporphyrins^9cis shown in Scheme 1.

Condensation of 2,5-bis(R-aryl- R-hydroxymethyl)thio-

(1) Some selected examples of covalently linked porphyrin arrays:

(a) Holten, D.; Bocian, D. F.; Lindsey, J . S. Acc. Chem. Res. 2002, 35,

57. (b) Palaniappan, V.; J ohnson, T. E.; Prathapan, S.; Lindsey, J . S.;

Bocia, D. J . Am. Chem. Soc. 1994, 116, 10578. (c) Wagner, R. W.;

J ohnson, T. E.; Li, F.; Lindsey, J . S. J . Org. Chem. 1995, 60, 5266. (d)

Hsiao, J .-S.; Krueger, B. P.; Wagner, R. W.; J ohnson, T. E.; Delaney,

J . K.; Mauzerall, D. C.; Fleming, G. R.; Lindsey, J . S.; Bocian, D. F.;

Donhoe, R. J . J . Am. Chem. Soc. 1996, 118, 11181. (e) Strachan, J .-P.;

Gentemann, S.; Seth, J .; Kalsbeck, W. A.; Lindsey, J . S.; Holten, D.;

Bocian, D. F. J . Am. Chem. Soc. 1997, 119, 1119. (f) Li, F.; Yang, S.-I.;

Ciringh, Y.; Seth, J .; Martin, C. H., III; Singh, D. L.; Kim, D.; Birge,

R. R.; Bocian, D. F.; Holten, D.; Lindsey, J . S. J . Am. Chem. Soc. 1998,

120, 10001. (g) Lin, V, S.-Y.; Dimagno, S. G.; Therien, M. J . Science

1994, 264, 1105. (h) Karki, L.; Vance, F. W.; Hupp, J . T.; LeCours, S.

M.; Therien, M. J . J . Am. Chem. Soc. 1998, 120, 2606. (i) Arnold, D.

P.; J ames, D. A. J . Org. Chem. 1997, 62, 3460. (j) Arnold, D. P.; J ames,

D. P.; Kolin, H. L.; Smith, G. J . Chem. Soc., Chem. Commun. 1994,

2131. (k) Burrell, A. K.; Officer, D. L.; Reid, D. C. W.; Wild, K. Y.

Angew. Chem., Int. Ed. 1998, 37, 114. (l) Burrell, A. K.; Officer, D. L.;

Plieger, P. G.; Reid, D. C. Chem. Rev. 2001, 101, 2751. (m) Osuka, A.;

Nakajima, S.; Okada, T.; Taniguchi, S.; Nozaki, K.; Ohno, T.; I.

Yamazaki, I.; Nishimura, Y.; Mataga, N. Angew. Chem., Int. Ed. Engl.

1996, 35, 92. (n) Yoshida, N.; Ishizuka, T.; Youfu, K.; Murakami, M.;

Miyasaka, H.; Okada, T.; Nagata, Y.; Itaya, A.; Cho, H. S.; Kim, D.;

Osuka, A. Chem. sEur. J . 2003, 9, 2854. (o) Osuka, A.; Fujikane, D.;

Shinmori, H.; Kobatake, S.; Irie, M. J . Org. Chem. 2001, 66, 3913. (p)

Mak, C. C.; Bampos, N.; Sanders, J . K. M. J . Angew. Chem. Int. Ed.

1998, 37, 3020. (q) Sessler. J . L.; Capuano, V. L.; Harriman, H. J .; J .

Am. Chem. Soc. 1993, 115, 4618. (r) Kuciauskas, D.; Liddell, P. A.;

Lin, S.; J ohnson, T. E.; Weghorn, J . S.; Lindsey, J . S.; Moore, A. L.;

Moore, T. A.; Gust. D. J . Am. Chem. Soc. 1999, 121, 8604. (s) Mongin,

O.; Papamicael, C.; Hoyler, N.; Gossauer, A. J . Org. Chem. 1998, 63,

5568. (t) Paolesse, R.; J aquinod, L.; Sala, F. D.; Nurco, D. J .; Prodi, L.;

Montalti, M.; Natale, C. D.; D’Amico, A.; Di Carlo, A.; Lugli, P.; Smith,

K. M. J . Am. Chem. Soc. 2000, 122, 11295. (u) Beavington, R.; Burn,

P. L. J . Chem. Soc. Perkin Trans. 1 2000, 1231. (v) Sugiura, K-i.;

Matsumoto, T.; Ohkouchi, S.; Naitoh, Y.; Kawai, T.; Takai, Y.;

Ushiroda, K.; Sakata, Y. J . Chem. Soc., Chem. Commun. 1999, 1957.

(w) Crossley, M. J .; Thordarson, P. Angew. Chem. Int. Ed. 2002, 41,

1709. (x) Crossley, M. J .; J ohnston, L. A. J . Chem. Soc., Chem.

Commun. 2002, 1122. (y) Vidal-Ferran, A.; Clyde-waston, Z.; Bampoos,

N.; Sanders, J . K. M. J . Org. Chem. 1997, 62, 240 (z) Bampos, N.;

Marvaud, V.; Sanders, J . K. M. Chem. sEur. J . 1998, 4, 335.

(6) (a) Pandian, R. P.; Chandrashekar, T. K. Inorg. Chem. 1994, 33,

3317. (b) Ravikumar, M.; Pandian, R. P.; Chandrashekar, T. K. J .

Porphyrins Phthalocyanines 1999, 3, 70.

(7) (a) Ravikanth, M. Tetrahedron Lett. 2000, 41, 3709. (b) Kumare-

san, D.; Agarwal, N.; Ravikanth, M. J . Chem. Soc., Perkin Trans. 1

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2000, 836.

(8) Santra, S.; Kumaresan, D.; Agarwal, N.; Ravikanth, M. Tetra-

hedron 2003, 59, 2353.

J . Org. Chem, Vol. 69, No. 20, 2004 6797

Gupta and Ravikanth

SCHEME 2. Lin d sey a n d Co-Wor k er s Syn th etic Sch em e for th e P r ep a r a tion of Mon ofu n ction a lized

21-Th ia a n d 21-Oxa p or p h yr in Bu ild in g Block s

Furthermore, Cho and co-workers¹¹developed a very

novel and rational method for the synthesis of 21-thia

and 21-oxaporphyrins containing two types of meso-

substituents in trans configuration. They further ex-

tended the same strategy to synthesize monofunctional-

ized 21-thia and 21-oxaporphyrins. Thus, 21-thia and 21-

oxaporphyrin having ethyne and iodo functional groups

at the para position of meso-phenyl group were synthe-

sized by this method as shown in Scheme 2. As evident

from the scheme, the method requires two key precursors

and involves multistep synthesis, extensive chromatog-

raphy, and vacuum distillations to purify the intermedi-

ate compounds.

Resu lts a n d Discu ssion

Syn th esis of Th iop h en e Mon o-ols 1-9 a n d F u r a n

Mon o-ols 10-12. The preparation of the mono- and

trifunctionalized 21-thia and 21-oxaporphyrin building

blocks depends on the availability of the suitable thiophene

and furan mono-ols which are key precursors in this

reaction. A series of thiophene mono-ols were prepared

by treating thiophene with 1.2 equivalents of n-butyl-

lithium followed by 1.2 equivalents of benzaldehyde or

substituted benzaldehyde in THF at 0 °C (Scheme 3).

The TLC analysis of the crude reaction mixture showed

two clear spots corresponding to the unreacted aldehyde

and the desired thiophene mono-ol. The crude compound

was subjected to silica gel column chromatography and

the fast moving unreacted aldehyde was collected as a

first band with petroleum ether/2-15% ethyl acetate. The

required thiophene mono-ol was always moved as a

second band and collected with petroleum ether/5-25%

ethyl acetate. The solvent was removed on a rotary

evaporator under vacuum and the oily compound had

been stored in a refrigerator overnight and a white solid

formed. Attempts to recrystallize the crude compound

without subjecting it first to column chromatography did

not afford the pure thiophene mono-ols. Thus, the column

chromatography is essential to afford pure thiophene

mono-ols in 65-70% yields. Similarly, the furan mono-

ols 10-12 were prepared by treating furan with 1.2

equivalents of n-butyllithium followed by 1.2 equivalents

of appropriate aldehyde under same reaction conditions.

However, the crude reaction mixture showed more com-

plex TLC with at least four spots unlike thiophene mono-

ols. Usually, the third spot on TLC was our desired furan

mono-ol. The crude mono-ols were subjected to silica gel

column chromatography and afforded the pure furan

mono-ols 10-12 as gray white solids in 50-70% yields.

The low yields observed in some cases such as 2, 3, and

10 were due to poor solubility of the corresponding

aldehydes. However, all these mono-ols can be prepared

easily in multigram quanity and purified by straightfor-

ward column chromatoghaphy. The thiophene and furan

mono-ols were characterized by mp, IR, elemental analy-

sis, and ¹H and ¹³C NMR spectroscopic techniques

(Supporting Information). The presence of a sharp singlet

for the CH proton in the region 5.6-5.9 ppm and broad

singlet for OH in 2.6-2.9 ppm region in the ¹H NMR and

We recently developed a one-step rapid synthetic route

to prepare mono- and trifunctionalized 21-thiaporphyrins

using a very easily available precursor such as 2[R-(aryl)-

R-hydroxymethyl] thiophene (thiophene mono-ol).¹²The

mono-ol method is versatile and gives an access to several

mono- and trifunctionalized 21-thiaporphyrins which

were not accessible earlier. In this paper, we describe in

detail the synthesis and characterization of a series of

thiophene or furan mono-ols and one-pot synthesis of

several mono- and trifunctionalized 21-thia and 21-

oxaporphyrins. We also showed the application of these

mono- and trifunctionalized 21-thia and 21-oxaporphyrin

building blocks in the synthesis of five covalently con-

nected unsymmetrical porphyrin dimers with different

combinations of porphyrin cores such as N₄-N₃S, N₄-

N₃O, and N₃S-N₃O as well as noncovalently connected

unsymmetrical porphyrin tetramers composed of one N₃S

porphyrin subunit and three N₄porphyrin subunits.

(9) (a) Latos-Grazynski, L.; Lisowski, J .; Olmstead, M. M.; Balch,

A. L. J . Am. Chem. Soc. 1987, 109, 4428. (b) Latos-Grazynski, L.;

Lisowski, J .; Szterenberg, L.; Olmstead, M. M.; Balch, A. L. J . Org.

Chem. 1991, 56, 4043. (c) Gross, Z, Saltsman, I.; Pandian, R.; Barzilay,

C. M. Tetrahedron Lett. 1997, 38, 2383.

(10) (a) Kumaresan, D.; Gupta, I.; Ravikanth, M. Tetrahedron Lett.

2001, 42, 8547. (b) Kumaresan, D.; Santra, S.; Ravikanth, M. Synlett

2001, 1635. (c) Kumaresan, D.; Agarwal, N.; Gupta, I.; Ravikanth, M.

Tetrahedron 2002, 58, 5347. (d) Gupta, I.; Ravikanth, M. Tetrahedron

2003, 59, 6131. (e) Gupta, I.; Hung, C.-H.; Ravikanth, M. Eur. J . Org.

Chem. 2003, 4392.

(11) (a) Cho, W.-S.; Kim, H.-J ., Littler, B. J .; Miller, M. A.; Lee, C.-

H.; Lindsey, J . S. J . Org. Chem. 1999, 64, 7890. (b) Lee. C.-H.; Park,

J .-Y.; Kim, H.-J . Bull. Korean Chem. Soc. 2000, 21, 97.

(12) Gupta, I.; Agarwal, N.; Ravikanth, M. Eur. J . Org. Chem. 2004,

1693.

6798 J . Org. Chem., Vol. 69, No. 20, 2004

One-Flask Synthesis

SCHEME 3. Syn th esis of Th iop h en e Mon o-ols 1-9

a n d F u r a n Mon o-ols 10-12

SCHEME 4. Syn th esis of Mon ofu n ction a lized

21-Th ia a n d 21-Oxa p or p h yr in s

strong peak at ∼3300 cm^-1for OH in IR were charac-

teristic features of thiophene and furan mono-ols. The

ES-MS spectra showed a weak peak of M⁺ion (10%) and

strong peak at M⁺-17 (90%) confirming the identities of

products.

Syn th esis of Mon ofu n ction a lized 21-Th ia a n d 21-

Oxa p or p h yr in s 13-23. 21-Thia and 21-oxaporphyrin

building blocks bearing one functional group provide the

basis for the synthesis of dimeric arrays. A series of

monofunctionalized 21-thia and 21-oxaporphyrins 13-

23 were synthesized using thiophene or furan mono-ols

in one-pot reaction as shown in Scheme 4. The condensa-

tion of two equivalents of thiophene or furan mono-ol with

two equivalents of aldehyde and three equivalents of

pyrrole in propionic acid¹³at refluxing temperature for

2 h, followed by the removal of propionic acid under

vacuum and thorough washing with warm water, gave

a crude mixture of two porphyrins: the desired mono-

functionalized 21-thia or 21-oxaporphyrin and tetra-aryl

substituted normal porphyrin (N₄). Absorption spectros-

copy was used to confirm the formation of the above two

porphyrins in every porphyrin condensation reaction

since absorption bands of 21-thia or 21-oxaporphyrins are

quite different from normal porphyrin. Although the

absorption spectra of the crude porphyrin mixture mainly

show absorption bands corresponding to N₄porphyrin, a

characteristic peak around ∼680 nm confirms the forma-

tion of N₃S or N₃O porphyrin. The crude porphyrin

mixture was initially subjected to silica gel column

chromatography and removed nonporphyrinic impurities.

The TLC analysis of porphyrin mixture after the first

column clearly showed two spots corresponding to N₄and

N₃S or N₃O porphyrins. The porphyrin mixture was

subjected to second silica gel column chromatography and

the desired 21-thia or 21-oxaporphyrin building blocks

13-23 were always collected as a second band and

afforded purple compounds in 2-7% yields. When we

performed porphyrin condensations under Lindsey et al.

conditions,¹⁴the yields of the desired 21-thia or 21-

oxaporphyrin building blocks were not improved. Al-

though the yields of monofunctionalized building blocks

are relatively low, the method is very simple and the

desired porphyrin building block with any functional

(13) Adler, A. D.; Longo, F. R.; Finarelli, J . D.; Goldmacher, J .;

Assour, J .; Korsakoff, L. J . Org. Chem. 1967, 32, 476.

(14) Lindsey, J . S.; Schreiman, I. C.; Hsu, H. C.; Kearay, P. C.;

Marguerettaz, A. M. J . Org. Chem. 1987, 52, 827.

J . Org. Chem, Vol. 69, No. 20, 2004 6799

Gupta and Ravikanth

SCHEME 5. Syn th esis of Tr ifu n ction a lized

group can be obtained very easily. Furthermore, since

the precursor thiophene or furan mono-ol can be synthe-

sized in multigram quantity, the desired porphyrin

building block can be obtained in ca. 100-mg quantities

in one-pot reaction. We varied the number of equivalents

of thiophene or furan mono-ol, aldehyde, and pyrrole to

optimize the porphyrin yields. When we used one equiva-

lent of thiophene or furan mono-ol keeping aldehyde and

pyrrole equivalents constant, the N₄porphyrin was

formed as a major product with trace amounts of the

required N₃S or N₃O porphyrin. When three equivalents

of thiophene or furan mono-ol was used, the yield of N₃S

or N₃O porphyrin did not increase. We also varied the

aldehyde and pyrrole equivalents keeping the mono-ol

equivalents constant but the yields were not improved.

Thus, two equivalents of thiophene or furan mono-ol, two

equivalents of aldehyde, and three equivalents of pyrrole

were needed to afford the porphyrin building blocks in

reasonable yields. We arrived at this stoichiometry after

testing a series of trial reactions. Though no explaination

can be offered at this stage, this reaction works well when

we used the above-mentioned ratio of reactants. The

mono-ol method is versatile and any desired monofunc-

tionalized 21-thia and 21-oxaporphyrin building block can

be prepared by using this method. The thiophene or furan

mono-ol should contain the functionalized aryl group to

synthesize monofunctionalized N₃S or N₃O porphyrin.

The mono-ol method is unique and novel and to the best

of our knowledge, there are no reports on using mono-

ols for porphyrin reaction. The only report on use of

mono-ols is when Grazynski and co-workers¹⁵synthesized

5,10,15-triaryl-21,23-dioxacorrole by condensing one

equivalent of 2-phenylhydroxymethyl furan (furan mono-

ol) with one equivalent of 2,5-bis(arylhydroxymethyl)-

furan and two equivalents of pyrrole under mild acidic

conditions. We also anticipated the corrole formation in

our condensation reactions but we did not observe any

corrole in these reactions.

21-Th ia a n d 21-Oxa p or p h yr in Bu ild in g Block s

N₃S and N₃O porphyrins, respectively. Prior to our

communication,¹²there were no reports available on the

synthesis of trifunctionalized 21-thia and 21-oxaporphy-

rin building blocks. To synthesize the trifunctionalized

N₃S and N₃O porphyrin, the thiophene and furan mono-

ol, respectively, were condensed with the desired func-

tionalized aryl aldehyde and pyrrole in propionic acid in

the same stoichiometry used for monofunctionalized

compounds at refluxing temperature (Scheme 5).

The monofunctionalized 21-thia and 21-oxaporphyrin

building blocks 13-23 were characterized with ¹H and

¹³C NMR, ES-MS, elemental analysis, IR, absorption, and

emission spectroscopic techniques (Supporting Informa-

tion). All porphyrins showed M⁺ion peak in mass spectra

Thus, the desired aryl functional groups were incor-

porated in 21-thia and 21-oxaporphyrin building blocks

by using the appropriate functionalized aryl aldehyde.

By using the mono-ol method, we synthesized trifunc-

tionalized N₃S and N₃O porphyrins containing pyridyl

and iodophenyl groups at the meso positions which are

useful building blocks for noncovalent and covalent

porphyrin arrays, respectively. The trifunctionalized N₃S

and N₃O porphyrin building blocks were purified by

column chromataography and characterized by the stan-

1

confirming the product. In the H NMR, all N₃S porphy-

rins clearly showed two signals for the thiophene protons

unlike 5, 10, 15, 20-tetraphenyl-21-thiaporphyrin^4a(STP-

PH) which showed only one signal for thiophene protons

indicating the unsymmetric substitution of 21-thiapor-

phyrin building blocks. Similarly, unlike one signal

observed for furan protons in 5, 10, 15, 20-tetraphenyl-

21-oxaporphyrin^4a(OTPPH), the monofunctionalized 21-

oxaporphyrin showed two signals due to unsymmetric

substitution. Absorption spectra for N₃S and N₃O por-

phyrin building blocks exhibited one Soret and four

Q-bands and the peak positions were in close match with

STPPH and OTPPH, respectively.^4aElemental analyses

were also in agreement with the composition of the

expected porphyrin building blocks.

1

dard spectroscopic techniques. The H NMR spectra of

the trifunctionalized N₃S and N₃O porphyrins indicated

the unsymmetric substitution of the porphyrin. All por-

phyrins showed an M⁺ion peak in ES-MS spectra and

characteristic absorption and emission spectra (Support-

ing Information).

Syn th esis of Un sym m etr ica l Cova len t P or p h yr in

Dim er s. The monofunctionalized N₃S and N₃O porphy-

rins with functional groups such as iodophenyl, ethyn-

ylphenyl, bromophenyl, and hydroxyphenyl groups at the

meso position reported in this paper are highly desirable

to synthesize a series of covalently linked porphyrin

dimers. They are ideal porphyrin building blocks to

Syn th esis of Tr ifu n ction a lized 21-Th ia a n d 21-

Oxa p or p h yr in s 24-28. The thiophene and furan mono-

ols were also useful in the synthesis of trifunctionalized

(15) Pawlicki, M.; Latos-Grazynski, L.; Szterenberg, L. J . Org. Chem.

2002, 67, 5644.

6800 J . Org. Chem., Vol. 69, No. 20, 2004

One-Flask Synthesis

CHART 1

synthesize unsymmetrical covalent dimers containing

two different types of porphyrin cores. Porphyrin-

porphyrin dimers are of interest for investigating the

pairwise interactions of porphyrins in larger arrays. To

demonstrate the use of porphyrin building blocks re-

ported in this paper, we synthesized five aryl ethyne

bridged covalent dimers 29-33 by taking appropriate

N₃S and N₃O porphyrin building blocks (Chart 1). The

N₃S porphyrin 15 and N₃O porphyrin 22 with mono-

ethynylphenyl group at the meso position were synthe-

sized by deprotecting N₃S porphyrin 14 and N₃O por-

phyrin 21, respectively, at 80 °C with KOH in benzene/

methanol. The other required porphyrin building block,

5,10,15-tri(mesityl)-20-(4-iodophenyl) zinc(II) porphyrin

34 was synthesized by following the literature method.¹⁶

The dimers 29-33 were synthesized by following milder

palladium coupling conditions developed by Lindsey and

co-workers¹⁷during their investigation on synthesis of

aryl ethyne bridged porphyrin arrays.

judged by TLC analysis. The solvent was removed on

rotary evaporator and the crude reaction mixture was

loaded on alumina column and eluted with petroleum

ether/dichloromethane. The small amounts of triphenyl

arsine and unreacted porphyrin building blocks were

removed with petroleum ether/dichloromethane (70:30)

and the dimer with small amounts of impurities was

collected with petroleum ether/dichloromethane (20:80).

The impure dimer was subjected to a second alumina

column and the pure unsymmetrical dimer 29 containing

N₃S-N₄cores was collected with the same solvent

mixture as purple solid in 66% yield. Similarly, coupling

of 5,10,15-tri(mesityl)-20-(4-ethynylphenyl) zinc(II)¹⁶35

with the other N₃S porphyrin building block 20 under

the same palladium coupling conditions followed by

chromatography on alumina yielded pure unsymmetrical

dimer 30 containing N₃S-N₄cores as purple solid in 37%

yield. The symmetrical dimer 31 containing N₃S-N₃S

cores bridged via phenyl ethyne instead of diaryl ethyne

was prepared in 69% yield by coupling N₃S porphyrin

building block 15 with 5-bromo-10,15,20-tris(p-tolyl)-21-

thiaporphyrin¹⁸36 under the same mild palladium

coupling conditions. The unsymmetrical dimer 32 with

N₃O-N₄cores was prepared by coupling N₃O porphyrin

building block 22 with 34 and the dimer 33 with N₃S-

N₃O cores was prepared by coupling N₃S porphyrin

building block 15 with N₃O porphyrin building block 23

Thus, the dimer 29 was synthesized by coupling N₃S

porphyrin 15 with 34 in toluene/triethylamine at 35 °C

in the presence of Pd₂(dba)₃and AsPh₃. The progress of

the reaction was monitored with TLC and absorption

spectroscopy. The reaction was stopped after the disap-

pearance of major amounts of starting materials as

(16) Lindsey, J . S.; Prathapan, S.; J ohnson, T. E.; Wagner, R. W.

Tetrahedron 1994, 50, 8941.

(17) Wagner, R. W.; J ohnson, T. E.; Li, F.; Lindsey, J . S. J . Org.

Chem. 1995, 60, 5266.

(18) Agarwal, N.; Hung, C.-H.; Ravikanth, M. Eur. J . Org. Chem.

2003, 3737.

J . Org. Chem, Vol. 69, No. 20, 2004 6801

Gupta and Ravikanth

SCHEME 6. Syn th esis of Un sym m etr ica l Cova len t Dim er 33

under the same palladium coupling conditions (Scheme

6). All reactions worked smoothly and involved simple

column chromatography for purification. There is no need

to use any size exclusion chromatography as all of the

dimers were easily separated using alumina column

chromatography. The dimers 29-33 are highly soluble

in all common organic solvents and were characterized

by spectroscopic techniques. ES-MS spectrometry of all

five dimers showed molecular ion peak confirming the

the dimer 29 with those of individual monomeric units

indicates only minor differences suggesting that the two

porphyrin subunits in the dimer interact very weakly.

Similarly, the dimers 30, 32, and 33 were also character-

ized by comparing the ¹H NMR spectra with their

corresponding two porphyrin monomeric units. However,

the dimer 31 in which two N₃S porphyrin units joined at

the meso positions via a phenylethyne linker showed the

signals which were shifted because of strong interactions

between the two porphyrin units. The chemical shifts of

protons of N₃S porphyrin unit of the dimer 31 which has

an ethyne group directly at the meso position were

altered drastically and the chemical shifts of protons of

other N₃S porphyrin unit which has phenyl group at the

meso position were not affected as much. The thiophene

proton which was adjacent to ethyne linker was shifted

to downfield (10.52 ppm) and the other proton of thiophene

was shifted to upfield (9.54 ppm) compared to 10, 15, 20-

tris (p-tolyl)-21-thiaporphyrin (10.00 and 9.95 ppm).¹⁸The

pyrrole protons adjacent to ethyne linker were also

shifted to downfield by 0.4 ppm. The bridging phenyl

protons also experienced similar downfield shifts. Simi-

larly, the inner NH proton of the same N₃S unit of dimer

31 was shifted to downfield by 0.8 ppm whereas the NH

proton of the other N₃S unit remain unaffected.

1

compounds (Supporting Information). The H NMR spec-

troscopy has been used to characterize the dimers 29-

33 in detail. The resonances of the dimers were assigned

on the basis of the spectra observed for the two monomers

taken independently. For instance, in the dimer 29 one

would expect one set of multiplet for two thiophene

protons and three sets of signals for six pyrrole protons

of N₃S subunit because of its lower symmetry and also

expect one signal for pyrrole protons of N₄subunit

(Supporting Information). In the ¹H NMR of 29, the

multiplet resonance observed at 9.81 ppm is due to two

thiophene protons and three doublets at 8.79, 8.93, and

8.98 ppm were due to six pyrrole protons of N₃S porphy-

rin subunit. The strong singlet observed at 8.72 ppm was

due to eight pyrrole protons of the ZnN₄porphyrin

subunit. The meso phenyl ortho, meta protons and

bridging phenyl group protons appeared in the region

7.32-8.32 ppm methyl and octyloxy groups appeared in

the region 0.9-4.25 ppm. The NH proton of N₃S subunit

was observed at -2.60 ppm as a broad singlet. A

comparison of chemical shifts of the various protons of

Absor p tion Sp ectr a of Dim er s 29-33. The absorp-

tion spectra of dimers and their corresponding monomers

in toluene were measured at room temperature. A

comparison of the absorption spectra of dimer 29 with a

1:1 mixture of corresponding monomers is shown in

6802 J . Org. Chem., Vol. 69, No. 20, 2004

One-Flask Synthesis

F IGURE 1. UV-vis spectra of dimer 29 (s) and 1:1 mixture of 15 and 34 (---) recorded in toluene. The concentration used was

2 × 10^-6M. The fluorescence spectra (λ_ex) 550 nm) of dimer and 1:1 mixture is shown in inset.

Figure 1 indicating that the covalent dimer 29 shows the

absorption bands corresponding to both of the monomers.

In the Q-band region, the absorption spectrum of the

dimer 29 was almost identical to that of the 1:1 mixture.

However, the dimer 29 showed split Soret band compared

to 1:1 mixture of monomers indicating an interaction

between the subunits. The position, shape, and the width

of the Soret band in dimeric systems has been used as a

probe for estimating the size of coupling interaction

between the two chromophores. Unlike dimer 29, which

showed a split Soret band, the other four dimers 30-33

showed a broad Soret band with a bandwidth range of

16-34 nm (fwhm). The maximum broadened Soret band

was observed for dimer 31 (fwhm ) 34 nm) which also

showed a red shifted absorption spectra compared to the

1:1 mixture of corresponding monomers suggesting a

strong interaction between the porphyrinic subunits.

Em ission a n d Excita tion Sp ectr a of Dim er s 29-

33. The fluorescence spectra of dimers 29, 30, and 32

were recorded at 550 and 515 nm and the dimers 31 and

33 were recorded at 515 nm in toluene at room temper-

ature. The data of fluorescence yields of dimers 29-33

are presented in Table 1. Excitation of dimer 29 at 515

nm, where the N₃S porphyrin subunit absorbs strongly,

results in typical N₃S porphyrin emission with quantum

yield resembling that of monomeric STPPH.¹⁹Illumina-

tion of dimer 29 at 550 nm, where ZnN₄subunit absorbs

strongly, causes the emission of ZnN₄subunit to be

quenched by 95% and the strong emission from the N₃S

porphyrin subunit was observed. However, when 1:1

mixture of ZnN₄porphyrin 34 and N₃S porphyrin 15 was

excited at 550 nm, the strong emission was observed

mainly from ZnN₄porphyrin subunit. These results

indicated that there is an efficient energy transfer from

the ZnN₄subunit to the N₃S subunit in dimer 29. The

excitation spectrum recorded for 29 at λ_em) 750 nm

matching exactly with the absorption spectrum further

confirmed the efficient energy transfer between the

subunits. Similarly, dimer 30 showed an efficient energy

transfer from the ZnN₄porphyrin subunit to the N₃S

porphyrin subunit. Interestingly, the dimer 32 with ZnN₄

and N₃O subunits, on excitation at 550 nm, showed the

emission mainly from the ZnN₄subunit with a weak

emission from the N₃O subunit (Table 1). This indicates

that the energy transfer from ZnN₄unit to N₃O unit was

not efficient. In this system, the emission of ZnN₄subunit

was quenched only 30% suggesting an inefficient energy

transfer between the subunits.

In phenyl ethyne linked dimer 31, which is composed

of identical N₃S porphyrin units, the ethyne substitiuted

porphyrin is shifted to lower energy and is expected to

serve as energy acceptor. The porphyrin with the phenyl

substituents is energetically unperturbed and expected

to serve as a donor.²⁰Similar observations were indeed

made for dimer 31. Upon excitation of dimer 31 at 515

nm, where the N₃S subunit with the phenyl substituents

absorbs strongly, the main emission was observed from

the N₃S subunit with the ethyne substituent indicating

an efficient energy transfer from one N₃S subunit to

another N₃S subunit (Table 1).

The emission spectrum recorded for dimer 33 contain-

ing N₃S and N₃O porphyrin subunits showed peak

maxima at 687 and 750 nm. The excitation spectrum

recorded at 750 nm is matching with the absorption

spectrum of the dimer indicating that it is true emission.

Since the energy levels of N₃S and N₃O porphyrin are

close, the energy-transfer dynamics in this dimer cannot

be understood with this preliminary study. Although the

steady-state fluorescence studies indicated the possibility

of energy transfer in the four dimers reported here,

detailed time-resolved studies are required to quantify

these energy-transfer dynamics.

Syn th esis of Un sym m etr ica l Non cova len t P or -

p h yr in Ar r a ys. The core-modified porphyrins with

pyridyl groups at the meso positions are excellent build-

ing blocks to construct noncovalent unsymmetrical por-

phyrin arrays. We earlier demonstrated the utility of cis-

pyridyl building blocks with the N₃S core in the construc-

tion of noncovalent trimer containing one N₃S porphyrin

and two N₄porphyrin cores.⁸Interestingly, except our

own report,⁸most of the metal-pyridyl based noncovalent

porphyrin arrays were limited to N₄porphyrins.^2a,bWe

used the N₃S porphyrin building blocks 25 and 26 with

(19) Pandian, R. P.; Chandrashekar, T. K.; Saini, G. S. S.; Verma,

A. L. J . Chem. Soc., Faraday Trans. 1993, 89, 677.

(20) Tomizaki, K-y.; Lysenko, A. B.; Taniguchi, M.; Lindsey, J . S.

Tetrahedron 2004, 60, 2011.

J . Org. Chem, Vol. 69, No. 20, 2004 6803

Gupta and Ravikanth

TABLE 1. F lu or escen ce Da ta of Cova len t Dim er s 29-33

Recor d ed in Tolu en e a t Excita tion Wa velen gth s 515 a n d

550 n m

chromatography on silica using petroleum ether/dichlo-

romethane (60:40) gave pure tetramers 37 in 17% yield

and 38 in 20% yield as purple solids. The porphyrin

tetramers 37 and 38 were highly soluble in all common

organic solvents and characterized by NMR, mass, ele-

mental, infrared, and UV-visible spectroscopic tech-

niques. The ¹H NMR spectrum of tetramer 37 comparing

with monomeric N₃S porphyrin is shown in Figure 2. The

¹H NMR spectra of tetramers 37 and 38 are composed of

signals from RuTPP(CO) subunit and N₃S porphyrin

compound

φ₅₁₅

φ₅₅₀

STPPH

OTPPH

ZnTPP

29

0.0168

0.0758

0.033

N₃Sem

ZnN₄em

N₃Sem

ZnN₄em

N₃Sem^a

N₃Oem

0.0182

0.0202

0.0079

0.0015

0.0090

0.0057

30

1

31

32

0.0199

0.0529

subunit 25 and 26, respectively. In the H NMR spectra

0.0152

0.0233

of the tetramers, the chemical shifts of the RuTPP(CO)

subunit remain unaltered and the clear evidence of

metal-pyridyl nitrogen coordination comes mainly from

the dramatic changes in the chemical shifts of the N₃S

porphyrin subunit.⁸The large upfield shifts of the 2,6-

and 3,5/4,5-pyridyl protons, â-pyrrole, â-thiophene, and

inner NH protons of N₃S subunit of tetramers support

their formation (Supporting Information). The changes

in the chemical shifts of N₃S porphyrin subunit of

tetramer 37 compared to N₃S porphyrin building block

25 are as follows: The 2,6-pyridyl protons of 25 which

appeared as two multiplets at 9.05 and 9.09 ppm were

upfield shifted in tetramer 37 to 1.78 and 1.86 ppm,

respectively. Similarly, the 3,5- pyridyl protons of N₃S

subunit in tetramer 37 were upfield shifted compared to

25. The â-pyrrole and â-thiophene protons of N₃S subunit

of tetramer 37 also experienced similar upfield shifts

compared to 25 (Supporting Information). The inner NH

proton that appears at -2.84 ppm in 25 was shifted to

-4.33 ppm in tetramer 37. Similar shifts were observed

for N₃S subunit of tetramer 38 compared to N₃S porphy-

ZnN₄em

33

N₃S + N₃Oem^b

0.0309

a

The emission bands of monomers N₃S porphyrin with ethyne

at the meso position and N₃S porphyrin with the meso aryl

although different in emission peak maxima are not distinguish-

b

able in dimer 31. Hence, the total quantum yield is given. The

emission peak maxima of N₃S and N₃O porphyrins are close and

indistinguishable in dimer 33.

three 4-pyridyl or 3-pyridyl groups at the meso positions

to construct unsymmetrical noncovalent porphyrin tet-

ramers 37 and 38, respectively, containing one N₃S

porphyrin subunit and three N₄subunits (Scheme 7).

To synthesize unsymmetrical noncovalent porphyrin

tetramers 37 and 38, we treated one equivalent of 25 and

26, respectively, with 3.2 equivalents of RuTPP(CO)-

(EtOH) in toluene at refluxing temperature for overnight.

As noted previously, the color of the reaction mixture

changed from bright red to brownish red as the reaction

progressed. The reaction was stopped after the comple-

tion of the reaction as judged by the TLC. Column

SCHEME 7. Syn th esis of Un sym m etr ica l Non cova len t Tetr a m er s 37 a n d 38

6804 J . Org. Chem., Vol. 69, No. 20, 2004

One-Flask Synthesis

F IGURE 2. ¹H NMR spectra of 25 and noncovalent tetramer 37 recorded in CDCl₃. The NH signals are shown in insets.

rin building block 26 (Supporting Information). Similar

results indicate the coordination of pyridyl groups of N₃S

porphyrin 25 and 26 to the ruthenium ion of the RuTPP-

(CO) core to form tetramers 37 and 38, respectively.

Further evidence for tetramer formation was obtained

from ES-MS spectra that has shown a clear M⁺ion peak,

and the elemental analysis also matched with the

composition. The infrared measurements on 37 and 38

showed a strong ν_(CO)stretch at ∼1953 cm^-1. The absorp-

tion spectra of 37 and 38 showed that absorption bands

correspond to both RuTPP(CO) subunit as well as N₃S

porphyrin subunits. Since the number of RuTPP(CO)

subunits are three in tetramer, the absorption bands that

correspond to RuTPP(CO) subunit are dominating the

absorption spectra of tetramers 37 and 38.

the monofunctionalized 21-thia and 21-oxoporphyrins.

Furthermore, the same mono-ol precursor can also be

used to synthesize the trifunctionalized N₃S and N₃O

porphyrin systems. We synthesized a series of trifunc-

tionalized 21-thia and 21-oxaporphyrin building blocks

using the same methodology.

To show the use of mono- and trifunctionalized N₃S

and N₃O porphyrin building blocks, we synthesized

unsymmetrical covalent and noncovalent porphyrins

arrays containing two different types of porphyrin cores.

We synthesized the first diaryl ethyne bridged four

unsymmetrical dimers containing N₃S or N₃O core and

N₄core and one symmetrical phenyl ethyne bridged

dimer containing two N₃S cores by following well-

established mild palladium coupling conditions. A pre-

liminary steady-state fluorescence study was carried out

on all five dimers. In dimers 29 and 30 containing N₃S

and ZnN₄units, an efficient energy transfer was observed

from the ZnN₄unit to the N₃S unit on selective excitation

of ZnN₄subunit. An efficient energy transfer was also

noted between two N₃S units in the phenylethyne bridged

symmetrical dimer 31. However, in dimer 32 containing

ZnN₄and N₃O subunits, the energy transfer from ZnN₄

unit to N₃O unit was not efficient and it was difficult to

understand the energy-transfer dynamics in dimer 33

Su m m a r y

In summary, we developed a simple and rapid method

to synthesize monofunctionalized 21-thia and 21-oxopor-

phyrin building blocks using an easily available thiophene

and furan mono-ols. The mono-ol method reported in this

paper is novel and applicable to synthesize any desired

monofunctionalized N₃S and N₃O porphyrins. This is the

first such method in which the simple precursors such

as thiophene or furan mono-ols were used to synthesize

J . Org. Chem, Vol. 69, No. 20, 2004 6805

Gupta and Ravikanth

134-136 °C. IR (KBr film, cm^-1) 3394, 3397 (OH). ¹H NMR

(400 MHz, CDCl₃, δ in ppm) 1.67 (br s, 1H), 5.98 (br s, 1H),

6.01 (s, 1H), 6.87 (m, 4H), 7.29 (m, 3H). ¹³C NMR (75 MHz,

CDCl₃): δ 21.3, 72.3, 124.8, 125.3, 126.4, 126.7, 129.3, 137.8,

140.4, 148.5. ES-MS: C₁₁H₁₀SO₂, calcd av mass 206.3, obsd

m/z 206.8 (M⁺, 10%), 189.0 (M⁺-17, 90%). Anal. calcd: C, 64.05;

H, 4.89; S, 15.55. Found: C, 63.78; H, 4.68; S, 15.28.

2-[r-(4-Oct yloxyp h en yl)-r-h yd r oxym et h yl]t h iop h en e

(4). The condensation of 2-lithiothiophene with 4-octyloxy

benzaldehyde (7.1 g, 30.418 mmol) under the same experi-

mental conditions as mentioned for 1 followed by silica gel

column chromatography using petroleum ether/ethyl aceate

(90:10) gave compound 4 as light-pink solid (3.4 g, 42%). M.

P. 45-47 °C. IR (KBr film, cm^-1) 3439 (OH). ¹H NMR (400

MHz, CDCl₃, δ in ppm) 0.88 (t, 3H), 1.34 (m, 8H), 1.44 (m,

2H), 1.77 (m, 2H), 2.44 (br s, 1H), 3.95 (m, 2H), 5.98 (s, 1H),

6.89 (m, 4H), 7.22 (m, 1H), 7.30 (m, 2H). ¹³C NMR (75 MHz,

CDCl₃): δ 14.2, 22.7, 26.1, 29.3, 29.4, 31.9, 68.1, 72.2, 114.5,

containing N₃S and N₃O cores. The understanding of the

photodynamics of this kind of unsymmetrical dimers will

be useful in designing efficient molecular photonic de-

vices. Two noncovalent unsymmetrical porphyrin tet-

ramers 37 and 38 containing one N₃S porphyrin subunit

and three N₄porphyrin subunits were also synthesized

to demonstrate the use of trifunctionalized porphyrin

building blocks. A detailed photodynamics of these novel

arrays is presently under investigation in our laboratory.

Exp er im en ta l Section

Th iop h en e a n d F u r a n Mon o-ols. 2-[r-(4-Br om op h en -

yl)-r-h yd r oxym eth yl]th iop h en e (1). Dry, distilled ether (40

mL) was added to a 250-mL three-necked, round-bottomed

flask fitted with a rubber septum and gas inlet tube; the flask

was flushed with argon for 10 min. Tetramethylethylenedi-

amine (TMEDA) (3.5 g, 4.6 mL, 30.418 mmol) and n-butyl-

lithium (20 mL of ca. 15% solution in hexane) were added to

the stirred solution and the reaction temperature maintained

at 0° C in an ice bath. Thiophene (2.1 g, 2.0 mL, 25.348 mmol)

was added and the solution was stirred for 1 h. As the reaction

progressed, a white turbid solution formed indicating the

formation of 2-lithiated salt of thiophene. An ice cold solution

of 4-bromobenzaldehyde (5.6 g, 30.418 mmol) in dry THF (40

mL) was then added and stirred for an additional 15 min at 0

°C. The reaction mixture was brought to room temperature.

The reaction was quenched by adding an ice-cold NH₄Cl

solution (50 mL, ca. 1 M). The organic layer was diluted with

ether and washed several times with water and brine and

dried over anhydrous Na₂SO₄. The solvent was removed in a

rotary evaporator under reduced pressure to afford the crude

compound. TLC analysis showed two spots mainly correspond-

ing to unchanged aldehyde and the desired mono-ol. The crude

compound was loaded on silica and eluted with petroleum

ether. The unchanged aldehyde was removed with petroleum

ether/ethyl acetate (98: 2) solvent mixture and the desired

mono-ol 1 was collected with petroleum ether/ethyl acetate (95:

5) solvent mixture. The solvent was removed in a rotary

evaporator to afford 1 as a white solid (5.0 g, 73% yield). M.

P. 59-61 °C. IR (KBr film, cm^-1) 3282 (OH). ¹H NMR (400

MHz, CDCl₃, δ in ppm) 2.82 (br s, 1H), 5.92 (s, 1H), 6.83 (d, J

) 3.6 Hz, 1H), 6.91 (t, 1H), 7.25 (m, 3H), 7.44 (d, J ) 8.4 Hz,

2H). ¹³C NMR (75 MHz, CDCl₃): δ 71.7, 121.9, 125.1, 125.8,

126.8, 128.0, 131.6, 142.06, 147.5. ES-MS: C₁₁H₉SOBr, calcd.

av mass 269.2, obsd m/z 270.3 (M⁺, 10%), 252.9 (M⁺-17, 90%).

Anal. calcd: C, 49.09; H, 3.37; S, 11.91. Found: C, 48.95; H,

3.04; S, 11.69.

2-[r-(p-3-Meth yl-3-h yd r oxybu t-1-yn -1-yl)p h en yl-r-h y-

d r oxym eth yl]th iop h en e (2). The 2-lithiothiophene which

was prepared similarly as mentioned above was condensed

with p-(3-methyl-3-hydroxybut-1yn-1-yl)benzaldehyde (5.7 g,

30.418 mmol) under the same experimental conditions men-

tioned for 1 and gave a crude compound. The crude compound

was subjected to silica gel column chromatography and the

desired mono-ol 2 was eluted with petroleum ether/ethyl

acetate (80:20) to give a white solid in 35% yield (2.4 g). M. P.

78-80 °C. IR (KBr film, cm^-1) 3265, 3370 (OH). ¹H NMR (400

MHz, CDCl₃, δ in ppm) 1.57 (s, 6H), 2.81 (s, 1H) 5.94 (s, 1H),

6.81 (d, J ) 3.6 Hz, 1H), 6.89 (t, 1 H), 7.21 (d, J ) 4.8 Hz, 1H),

7.32 (m, 4H). ¹³C NMR (75 MHz, CDCl₃): δ 30.1, 31.6, 65.7,

76.3, 81.9, 94.4, 126.0, 126.2, 126.3, 126.6, 126.7, 127.0, 127.2,

141.1, 145.3, 145.4. ES-MS: C₁₆H₁₆SO₂, calcd av mass 272.4,

obsd m/z 273.1 (M⁺, 10%). Anal. calcd: C, 70.56; H, 5.92; S,

11.77. Found: C, 70.35; H, 5.57, S,11.45.

124.7, 125.3, 126.6, 127.7, 135.3, 148.6, 159.01. ES-MS: C₁₉H₂₆

-

SO₂, calcd av mass 318.5, obsd m/z 318.9 (M⁺,10%), 301.2 (M⁺-

17, 50%). Anal. calcd. C, 71.66; H, 8.23; S, 10.07. Found: C,

71.14; H, 8.36; S, 10.04.

2-[r-(2-Th ien yl)-r-h yd r oxym eth yl]th iop h en e (5). The

condensation of 2-lithiothiophene with 2-thienylaldehyde (3.4

g, 2.8 mL, 30.418 mmol) followed by column chromatography

using petroleum ether/ethyl acetate (95:5) gave mono-ol 5 as

a brown solid (2.8 g, 55% yield). M. P. 46-48 °C IR (KBr film,

1

cm^-1) 3447 (OH). H NMR (400 MHz, CDCl₃, δ in ppm) 2.71

(br s, 1H), 6.27 (s, 1H), 6.96 (m, 2H), 7.00 (m, 2H), 7.28 (d, J

) 4.88 Hz, 2H). ¹³C NMR (75 MHz, CDCl₃): δ 68.5, 72.5, 125.1,

125.5, 126.1, 126.2, 126.5, 126.7, 144.6, 147.2. ES-MS: C₉H₈S₂O,

calcd av mass 196.3, obsd m/z 196.9 (M⁺, 10%), 178.9 (M⁺-17,

90%). Anal. calcd. C, 55.07; H, 4.11; S, 32.67. Found: C, 54.91;

H, 3.96; S, 32.37.

2-[r-(2-6-Dim e t h oxyp h e n yl)-r-h yd r oxym e t h yl]t h io-

p h en e (6). The 2-lithiothiophene was prepared by treating

thiophene (0.5 g, 0.5 mL, 6.337 mmol) with n-BuLi (4.8 mL of

ca. 15% solution in hexane) in the presence of TMEDA (1.2

mL, 7.604 mmol) in ether (20 mL). The condensation of

2-lithiothiophene with 2-6-dimethoxybenzlaldehyde (1.3 g,

7.604 mmol) followed by column chromatography on silica

using petroleum ether/ethyl acetate (75:25) gave 6 as white

solid in 76% yield (1.2 g). M. P. 73-75 °C. IR (KBr film, cm^-1

)

3507 (OH). ¹H NMR (400 MHz, CDCl₃, δ in ppm) 3.79 (s, 6H),

4.66 (d, J ) 10.9 Hz, 1H), 6.45 (d, J ) 12.2 Hz, 1H), 6.59 (d,

J ) 8.5 Hz, 2H), 6.75 (d, J ) 3.7 Hz, 1H), 6.86 (t, 1H), 7.15 (d,

J ) 4.8 Hz, 1H), 7.22 (t, 1H). ¹³C NMR (75 MHz, CDCl₃): δ

55.9, 65.9, 104.6, 118.9, 123.6, 124.3, 126.5, 129.3, 149.5, 157.8.

ES-MS: C₁₃H₁₄SO₃, calcd av mass 250.3, obsd m/z 250.1 (M⁺,

10%), 233.1 (M⁺-17, 90%). Anal. calcd: C, 62.38; H, 5.64; S,

12.81. Found: C, 62.07; H, 5.32; S, 12.60.

2-[r-(p-Tolyl)-r-h yd r oxym eth yl]th iop h en e (7). The con-

densation of 2-lithiothiophene with p-tolylaldehyde (3.6 g, 3.5

mL, 30.418 mmol) followed by silica gel column chromatogra-

phy using petroleum ether/ethyl acetate (95:5) afforded mono-

ol 7 in 79% yield (4.1 g). M. P. 44-47 °C. IR (KBr film, cm^-1

)

3381 (OH). ¹H NMR (400 MHz, CDCl₃, δ in ppm) 2.34 (s, 3H),

2.50 (s, 1H), 5.98 (s, 1H), 6.86 (m, 1H), 6.92 (m, 1H), 7.16 (d,

J ) 7.6 Hz, 2H), 7.23 (m, 1H), 7.27 (d, J ) 7.6 Hz, 2H). ¹³C

NMR (75 MHz, CDCl₃): δ 21.3, 72.3, 124.8, 125.3, 126.4, 126.7,

129.3, 137.8, 140.4, 148.5. ES-MS: C₁₂H₁₂SO, calcd av mass,

204.3 obsd m/z 205.2 (M⁺, 10%), 187.1 (M⁺-17, 50%). Anal.

calcd: C, 70.55; H, 5.92; S, 15.70. Found: C, 70.17; H, 5.74; S,

15.52.

2-[r-P h en yl-r-h yd r oxym eth yl]th iop h en e (8). The con-

densation of 2-lithiothiophene with benzaldehyde (3.2 g, 3.2

mL, 30.418 mmol) followed by column chromatography on

silica using petroleum ether/ethyl acetate (95:5) gave 8 as

white solid (3.8 g, 77% yield). M. P. 53-55 °C. IR (KBr film,

2-[r-(4-Hydr oxyph en yl)-r-h ydr oxym eth yl]th ioph en e (3).

The condensation of 2-lithiothiophene with 4-hydroxybenzal-

dehyde (3.7 g, 30.418 mmol) under the same experimental

conditions mentioned for 1 followed by silica gel column

chromatography using petroleum ether/ethyl acetate (75:25)

gave compound 3 as white solid in 11% yield (0.6 g). M. P.

1

cm^-1) 3250 (OH). H NMR (400 MHz, CDCl₃, δ in ppm) 2.45

(br s, 1H), 6.05 (s, 1H), 6.88 (m, 1H), 6.92 (m, 1H), 7.27 (m,

1H) 7.36 (m, 3H), 7.44 (m, 2H). ¹³C NMR (75 MHz, CDCl₃): δ

6806 J . Org. Chem., Vol. 69, No. 20, 2004

One-Flask Synthesis

72.3, 124.8, 125.4, 126.4, 126.8, 129.3, 137.8, 140.4, 148.5. ES-

MS: C₁₁H₁₀SO, calcd av mass 190.3, obsd m/z 191.0 (M⁺, 10%),

173.0 (M⁺-17, 90%). Anal. calcd: C, 69.44; H, 5.30; S, 16.85.

Found: C, 69.38; H, 5.19; S, 16.83.

Mon ofu n ction a lized P or p h yr in Bu ild in g Block s. 5-(p-

Br om op h en yl)-10,15,20-tr i(p-tolyl)-21-m on oth ia p or p h y-

r in (13). The samples of thiophene mono-ol 1 (0.8 g, 2.972

mmol), p-tolylaldehyde (0.4 g, 0.35 mL, 2.972 mmol), and

pyrrole (0.3 g, 0.3 mL, 4.458 mmol) were dissolved in 80 mL

propionic acid and gently refluxed for 3 h. The progress of the

reaction was checked by absorption spectroscopy which showed

bands mainly characteristic of normal porphyrin (N₄core) with

slight indication of the desired N₃S porphyrin. The propionic

acid was removed under vacuum and the resultant black solid

was washed several times with warm water and dried in an

oven at 100 °C. The crude black solid was passed through silica

gel column using dichloromethane as solvent to remove

nonporphyrinic impurities. The TLC analysis of the compound

after the filtration column showed clearly two spots corre-

sponding to 5, 10, 15, 20-tetratolyl porphyrin (N₄) and the

desired N₃S porphyrin. The crude mixture of two compounds

was subjected to second silica gel column chromatography and

eluted with petroleum ether. The N₄porphyrin was collected

as first band with petroleum ether/dichloromethane (90:10)

and the desired porphyrin 13 was then collected using

petroleum ether/dichloromethane (80:20) mixture. The solvent

was removed in a rotary evaporator to afford 13 as purple solid

in 3% yield (20 mg). M. P. > 300 ° C. IR (neat, cm^-1) 3335

2-[r-(m -Iod op h en yl)-r-h yd r oxym eth yl]th iop h en e (9).

The 2-lithiothiophene was prepared by treating thiophene (0.6

g, 0.6 mL, 7.609 mmol) with n-BuLi (5.7 mL of ca. 15% solution

in hexane) in the presence of TMEDA (1.1 g, 1.4 mL, 9.131

mmol) in ether (20 mL). The 2-lithiothiophene was then

condensed with m-iodobenzaldehyde (2.1 g, 9.131 mmol) and

purified the resulted crude compound by column chromatog-

raphy on silica using petroleum ether/ethyl acetate (90:10)

gave compound 9 as white solid (1.4 g, 58% yield). M. P. 76-

78 °C. IR (KBr film, cm^-1) 3386 (OH). ¹H NMR (400 MHz,

CDCl₃, δ in ppm) 2.59 (br s, 1H), 5.95(s, 1H), 6.43 (m, 1H),

6.94 (m, 1H), 7.08 (t, 1H), 7.26 (m, 1H), 7.33 (m, 1H), 7.63 (m,

1H), 7.79 (m, 1H).¹³C NMR (75 MHz, CDCl₃): δ 71.5, 94.5,

125.2, 125.6, 125.9, 126.8, 130.3, 135.3, 137.0, 145.3, 147.3.

ES-MS: C₁₁H₉SOI, calcd av mass 316.2, obsd m/z 316.0 (M⁺,

10%), 299.0 (M⁺-17, 90%). Anal. calcd: C, 41.79; H, 2.87; S,

10.14. Found: C, 41.85; H, 2.59; S, 9.99.

2-[r-(-p-3-Meth yl-3-h yd r oxybu t-1yn -1-yl)p h en yl-r-h y-

d r oxym eth yl]fu r a n (10). The treatment of furan (2.8 g, 3.0

mL, 41.282 mmol) with n-BuLi (31 mL of ca. 15% solution in

hexane), TMEDA (5.8 g, 7.5 mL, 49.538 mmol) in 50-mL dry

ether under nitrogen atmosphere at 0 °C on ice bath for 1 h

gave 2-lithiofuran. An ice-cold solution of p-(3-methyl-3-

hydroxybut-1yn-1-yl)benzaldehyde (9.3 g, 49.538 mmol) in 50-

mL dry THF was then added and the reaction mixture was

allowed to stir for 15 min at 0 °C. The TLC analysis of crude

reaction mixture showed two major spots corresponding to the

unchanged aldehyde and the desired mono-ol. The crude

compound was purified by silica gel column chromatography

using petroleum ether/ethyl acetate (80:20) and obtained

mono-ol 10 as white solid (2.4 g, 23% yield). M. P. 81-83 °C.

1

(NH), 2920, 2854, 801. H NMR (300 MHz, CDCl₃, δ in ppm)

-2.70 (s, 1H), 2.69 (s, 9H), 7.54 (d, J ) 7.7 Hz, 4H), 7.62 (d, J

) 7.7 Hz, 2H), 7.94 (m, 2H), 8.09 (m, 8H), 8.62 (m, 3H), 8.69

(d, J ) 4.8 Hz, 1H), 8.95 (d, J ) 4.8 Hz, 2H), 9.67 (d, J ) 5.5

Hz, 1H), 9.76 (d, J ) 5.5 Hz, 1H). ¹³C NMR (100 MHz,

CDCl₃): δ 21.5, 29.7, 126.9, 127.4, 128.3, 128.5, 128.9, 130.7,

131.8, 132.5, 132.8, 133.1, 133.6, 134.2, 134.4, 134.6, 135.5,

135.8, 137.6, 138.0, 139.1, 139.5, 141.8, 146.9, 148.3, 154.6,

156.8, 157.6. ES-MS: C₄₇H₃₄N₃SBr, Calcd av mass, 752.7 obsd

m/z 752.7 (M⁺). Anal. calcd: C, 74.99; H, 4.55; N, 5.58; S, 4.26.

Found: C, 74.85; H, 4.47; N, 5.52; S, 4.22. UV-vis λ_max/nm

(ꢀ/mol^-1dm³cm^-1): 431 (335717), 487 (sh), 515 (24699), 550

(8644), 618 (3172), 679 (4866). Fluorescence: (λ_ex) 515 nm,

in toluene) λ_em/nm 684, 747 (sh), φ ) 0.0208.

5-(p-3-Meth yl-3-h yd r oxybu t-1-yn -1-yl)p h en yl)-10,15,20-

tr is(p-octyloxyp h e n yl)- 21-m on oth ia p or p h yr in (14). The

thiophene mono-ol 2 (3.5 g, 12.849 mmol), p-octyloxybenzal-

dehyde (3.0 g, 12.849 mmol), and pyrrole (1.3 g, 1.4 mL, 19.274

mmol) in 300 mL propionic acid were refluxed for 3 h. The

propionic acid was removed under vacuum and the black solid

was washed several times with warm water. The crude

compound was subjected to silica gel column chromatography

two times. After removing the nonporphyrinic impurities on

the first silica gel column, the mixture of two porphyrins were

separated on the second silica gel column and the desired N₃S

porphyrin 14 was collected as second band using dichlo-

romethane/methanol (99:1) mixture. The solvent was removed

in rotary evaporator and the compound 14 collected as soft

brown waxy solid in 6% yield (440 mg). IR (neat, cm^-1) 3335

(NH), 2927, 2855, 1242, 1176, 808. ¹H NMR (300 MHz, CDCl₃,

δ in ppm) -2.64 (s, 1H), 0.93 (m, 9H), 1.09-1.60 (m, 30H),

1.75 (s, 6H), 1.95 (m, 6H), 4.19 (m, 6H), 7.22 (m, 4H), 7.29 (d,

J ) 8.4 Hz, 2H), 7.86 (d, J ) 8 Hz, 2H), 8.06 (m, 4H), 8.12 (d,

J ) 8 Hz, 2H), 8.19 (d, J ) 7.6 Hz, 2H), 8.62 (s, 3H), 8.69 (d,

J ) 4.4 Hz, 1H), 8.95 (s, 2H), 9.68 (d, J ) 5.2 Hz, 1H), 9.76 (d,

J ) 5.2 Hz, 1H). ¹³C NMR (100 MHz, CDCl₃): δ 14.3, 22.9,

26.4, 29.5, 29.9, 31.8, 32.1, 65.9, 68.5, 82.3, 95.2, 112.8, 113.8,

122.4, 123.9, 124.2, 129.2, 130.0, 130.9, 131.7, 132.8, 133.8,

133.9, 134.3, 134.8, 135.7, 141.3, 147.2. ES-MS: C₇₃H₈₃N₃SO₄,

calcd av mass 1098.5, obsd m/z 1098.7 (M⁺). Anal. calcd: C,

79.81; H, 7.62; N, 3.83; S, 2.92. Found: C, 79.75; H, 7.59; N,

3.81; S, 2.90. UV-vis λ_max/nm (ꢀ/mol^-1dm³cm^-1): 434 (37049),

517 (4232), 552 (2689), 614(1152), 678 (1075). Fluorescence:

(λ_ex) 515 nm, in toluene) λ_em/nm 680, 746 (sh), φ ) 0.0287.

1

IR (KBr film, cm^-1) 3372 (OH). H NMR (400 MHz, CDCl₃, δ

in ppm) 1.61 (s, 6H), 2.30 (br s, 1H), 5.80 (s, 1H), 6.08 (d, J )

2.4 Hz, 1H), 6.31 (d, J ) 3.6 Hz, 1H), 7.37 (m, 5H). ¹³C NMR

(100 MHz, CDCl₃): δ 31.5, 65.73, 69.8, 81.9, 94.1, 107.7, 110.4,

122.5, 126.6, 127.4, 131.6, 131.8, 140.9, 142.8, 155.7. ES-MS:

C

₁₆H₁₆O₃, calcd av mass 256.3, obsd m/z 257.2 (M⁺,10%), 239.1

(M⁺-17, 90%). Anal. calcd: C, 74.98; H, 6.29. Found: C, 74.52;

H, 6.15.

2-[r-(p-Iod op h en yl)-r-h yd r oxym eth yl]fu r a n (11). The

2-lithiofuran was prepared by treating furan (1.8 g, 2 mL,

27.521 mmol) with n-BuLi (20.6 mL of ca. 15% solution in

hexane) in the presence of TMEDA (3.8 g, 4.9 mL, 33.025

mmol) in ether (40 mL). The condensation of 2-lithiothiophene

with p-iodobenzaldehyde (7.6 g, 33.025 mmol) followed by

column chromatography on silica using petroleum ether/ethyl

acetate (95:5) afforded furan mono-ol 11 as white solid (4.9 g,

59% yield). M. P. 134-136 °C. IR (KBr film, cm^-1) 3381 (OH).

¹H NMR (400 MHz, CDCl₃, δ in ppm) 2.56 (br s, 1H), 5.71 (s,

1H), 6.08 (m, 1H), 6.29 (m, 1H), 7.14 (m, 2H), 7.36 (m, 1H),

7.66 (m, 2H). ¹³C NMR (75 MHz, CDCl₃): δ 69.5, 93.7, 107.7,

110.3, 128.5, 128.8, 137.5, 137.6, 140.4, 142.8, 155.3. ES-MS

C

₁₁H₉O₂I, calcd av mass 300.1, obsd m/z 300.8 (M⁺, 10%). Anal.

calcd: C, 44.03; H, 3.02. Found: C, 43.87; H, 2.93.

2-[r-(4-Tolyl)-r-h yd r oxym eth yl]fu r a n (12). The 2-lithio-

furan (1.8 g, 2 mL, 27.521 mmol) which was prepared similarly

as above was condensed with p-tolyl aldehyde (4.0 g, 3.9 mL,

33.025 mmol) and purification by column chromatography

using petroleum ether/ethyl acetate (99:1) gave mono-ol 12 as

gray low-melting solid in 56% yield (2.9 g). IR (neat, cm^-1) 3341

1

(OH). H NMR (400 MHz, CDCl₃, δ in ppm) 2.35 (s, 3H), 2.39

(br s, 1H), 5.76 (s, 1H), 6.11 (d, J ) 3.6 Hz, 1H), 6.29 (d, J )

3.6 Hz, 1H), 7.17 (d, J ) 7.6 Hz, 2H), 7.30 (d, J ) 8.4 Hz, 2H),

7.37 (s, 1H). ¹³C NMR (75 MHz, CDCl₃): δ 21.3, 70.1, 107.4,

110.2, 110.3, 126.7, 127.6, 129.3. 137.9, 138.1, 142.6, 142.8,

156.3. ES-MS: C₁₂H₁₂O₂, calcd av mass 188.2, obsd m/z 189.2

(M⁺, 10%), 171.1 (M⁺-17, 90%). Anal. calcd: C, 76.57; H, 6.43.

Found: C, 76.52; H, 6.46.

5-(p-Eth yn ylp h en yl)-10,15,20-tr is (p-octyloxyp h en yl)-

21-m on oth ia p or p h yr in (15). Compound 14 (0.4 g, 0.364

mmol) was dissolved in dry benzene (50 mL) taken in one-

necked round-bottom flask fitted with Dean and Stark ap-

J . Org. Chem, Vol. 69, No. 20, 2004 6807

Gupta and Ravikanth

paratus and reflux condenser. The potassium hydroxide (0.03

g, 0.546 mmol) dissolved in methanol (25 mL) was added to

it, and the reaction mixture was stirred for 20 h at 80 °C. The

solvent mixture collected in Dean and Stark apparatus was

removed at regular intervals and the progress of reaction was

followed by TLC analysis. After completion of the reaction as

judged by TLC, the compound was purified by silica gel column

chromatography using petroleum ether/dichloromethane (30:

70) followed by recrystallization from acetone that afforded

15 as purple solid in 18% yield (70 mg). M. P. > 300 ° C. IR

(neat, cm^-1) 3335 (NH), 2927, 2855, 1242, 1183, 808. ¹H NMR

(300 MHz, CDCl₃, δ in ppm) -2.64 (s, 1H), 0.94 (m, 9H), 1.25-

1.66 (m, 30H), 1.97 (m, 6H), 3.31 (s, 1H), 4.22 (m, 6H), 7.24

(m, 4H), 7.32 (d, J ) 5.1 Hz, 2H), 7.93 (d, J ) 8.1 Hz, 2H),

8.07 (m, 4H), 8.13 (d, J ) 8.4 Hz, 2H), 8.21 (d, J ) 8.4 Hz,

2H), 8.62 (d, J ) 5.7 Hz, 3H), 8.69 (d, J ) 4.5 Hz, 1H), 8.95 (s,

2H), 9.67 (d, J ) 5.1 Hz, 1H), 9.76 (d, J ) 5.1 Hz, 1H). ¹³C

NMR (100 MHz, CDCl₃): δ 14.3, 22.9, 26.4, 29.5, 29.6, 30.0,

68.5, 112.8, 113.8, 121.8, 123.9, 124.2, 128.9, 129.1, 129.8,

131.4, 131.7, 132.7, 133.2, 133.3, 133.8, 134.3, 134.7, 135.5,

135.6, 135.8, 139.4, 139.6, 141.8, 146.9, 147.2, 154.7, 154.9,

156.9, 157.9, 159.2, 159.3. ES-MS: C₇₀H₇₇N₃SO₃, calcd av mass

1040.5, obsd m/z 1040.7 (M⁺). Anal. calcd: C, 80.81; H, 7.46;

N, 4.04; S, 3.08. Found: C, 80.69; H, 7.38; N, 4.03; S, 3.05.

UV-vis λ_max/nm (ꢀ/mol^-1dm³cm^-1): 434 (196826), 518 (12227),

554 (5996), 621(1615), 682 (3323). Fluorescence: (λ_ex) 515

nm, in toluene) λ_em/nm 690, 758 (sh), φ ) 0.0184.

682 (3323). Fluorescence: (λ_ex) 515 nm, in toluene) λ_em/nm

683, 752 (sh), φ ) 0.0154.

5-(2-Th ien yl)-10,15,20-tr i(p-tolyl)-21-m on oth ia p or p h y-

r in (18). Condensation of the thiophene mono-ol 5 (0.4 g, 2.038

mmol), p-tolylaldehyde (0.2 g, 0.2 mL, 2.038 mmol), and pyrrole

(0.2 g, 0.2 mL, 3.057 mmol) in 50 mL propionic acid at

refluxing temperature for 3 h. Column chromatography of the

crude compound on silica gel using petroleum ether/dichlo-

romethane (80:20) gave compound 18 in 2% yield (12 mg). M.

P. > 300 ° C. IR (neat, cm^-1) 3335 (NH), 2934, 2861, 801, 702.

¹H NMR (300 MHz, CDCl₃, δ in ppm) -2.59 (s, 1H), 2.70 (s,

9H), 7.55 (m, 5H), 7.62 (d, J ) 2.4 Hz, 2H), 7.90 (m, 1H), 7.94

(m, 1H), 8.07 (d, J ) 17.5 Hz, 4H), 8.13 (d, J ) 7.9 Hz, 2H),

8.61 (m, 2H), 8.67 (d, J ) 4.7 Hz, 1H), 8.87 (d, J ) 4.7 Hz,

1H), 8.92 (m, 2H), 9.76 (d, J ) 5.2 Hz, 1H), 9.96 (d, J ) 5.2

Hz, 1H). ¹³C NMR (100 MHz, CDCl₃): δ 21.7, 122.6, 124.4,

124.7, 127.2, 127.6, 128.5, 128.7, 129.0, 129.2, 132.2, 132.9,

133.2, 134.3, 134.4, 134.6, 134.8, 135.7, 135.8, 137.8, 138.2,

139.3, 139.5, 139.7,141.9, 147.2, 148.5, 154.7, 154.8, 157.8,

158.1. ES-MS: C₄₅H₃₃N₃S₂, calcd av mass 680.1, obsd m/z 681.1

(M⁺). Anal. calcd: C, 79.49; H, 4.89; N, 6.18; S, 9.43. Found:

C, 79.12; H, 4.68; N, 6.07; S, 9.32. UV-vis λ_max/nm (ꢀ/mol^-1

dm³cm^-1): 433 (344346), 517 (24169), 553 (9685), 620 (3349),

683 (4571). Fluorescence: (λ_ex) 515 nm, in toluene) λ_em/nm

693, 756 (sh), φ ) 0.0126.

5-(2,6-Dim eth oxyph en yl)-10,15,20-tr i(p-tolyl)- 21-m on o-

th ia p or p h yr in (19). Compound 6 (0.4 g, 1.598 mmol), p-

tolylaldehyde (0.2 g, 0.2 mL, 1.598 mmol), and pyrrole (0.2 g,

0.2 mL, 2.397 mmol) were dissolved in 50 mL propionic acid

and refluxed for 3 h. Column chromatography of the crude

compound on silica gel in petroleum ether/dichloromethane

(60:40) mixture gave compound 19 in 2% yield (12 mg). M. P.

> 300 ° C. IR (neat, cm^-1) 3335 (NH), 3026, 2927, 2835, 1591,

5-(p-Hydr oxyph en yl)-10,15,20-tr i (p-tolyl)-21-m on oth ia-

p or p h yr in (16). Condensation of thiophene mono-ol 3 (0.4 g,

1.939 mmol), p-tolylaldehyde (0.2 g, 0.2 mL, 1.939 mmol), and

pyrrole (0.2 g, 0.2 mL, 2.908 mmol) in 50 mL propionic acid at

refluxing temperature followed by standard workup gave a

crude compound. Column chromatography of the crude com-

pound on silica gel using dichloromethane/methanol (98:2)

mixture gave compound 16 as purple solid in 4% yield (20 mg).

M. P. > 300 °C. IR (neat, cm^-1) 3328 (NH), 2966, 2921, 2855,

1

1466, 1439, 1256, 1117, 802, 716. H NMR (400 MHz, CDCl₃,

δ in ppm) -2.52 (s, 1H), 2.64 (s, 9H), 3.47 (s, 6H), 6.94 (d, J )

8.4 Hz, 2H), 7.54 (m, 7H), 8.08 (m, 6H), 8.59 (m, 4H), 8.89 (s,

2H), 9.51 (d, J ) 5.2 Hz, 1H), 9.68 (d, J ) 5.2 Hz, 1H). ¹³C

NMR (100 MHz, CDCl₃): δ 21.6, 29.9, 56.2, 104.6, 118.6, 123.5,

123.9, 124.2, 127.4, 128.4, 128.5, 128.8, 130.6, 131.2, 132.7,

132.7, 133.9, 134.3, 134.5, 135.3, 135.6, 137.6, 138.4, 138.8,

139.3, 139.8, 139.9, 147.2, 147.9, 153.9, 154.6, 158.6, 160.1.

ES-MS: C₄₉H₃₉N₃SO₂, calcd av mass 733.9, obsd m/z 734.4

(M⁺). Anal. calcd: C, 80.19; H, 5.36; N, 5.73; S, 4.37. Found:

C, 80.10; H, 5.27; N, 5.69; S, 4.29. UV-vis λ_max/nm (ꢀ/mol^-1

dm³cm^-1): 430 (107607), 513 (8591), 547 (2015), 618 (1058),

679 (1419). Fluorescence: (λ_ex) 515 nm, in toluene) λ_em/nm

683, 752 (sh), φ ) 0.0158.

1

1268, 1025, 802. H NMR (300 MHz, CDCl₃, δ in ppm) -2.68

(s, 1H), 2.69 (s, 9H), 3.05 (br s, 1H), 7.54 (d, J ) 7.5 Hz, 6H),

7.61 (d, J ) 7.5 Hz, 2H), 8.09 (m, 8H), 8.60 (d, J ) 4.5 Hz,

2H), 8.64 (d, J ) 4.5 Hz, 2H), 8.93 (s, 2H), 9.75 (s, 2H). ¹³C

NMR (100 MHz, CDCl₃): δ 21.7, 29.5, 29.9, 115.5, 115.6, 116.2,

123.9, 126.6, 127.0, 127.6, 128.2, 128.6, 129.0, 129.3, 130.8,

131.5, 131.9, 132.1, 132.9, 133.2, 133.7, 134.5, 134.7, 135.8,

137.0, 137.8, 139.7. ES-MS: C₄₇H₃₅N₃SO, calcd av mass 689.9,

obsd m/z 690.5 (M⁺). Anal. calcd: C, 81.83; H, 5.11; N, 6.09;

S, 4.65. Found: C, 81.75; H, 5.06; N, 6.01; S, 4.59. UV-vis

λ

_max/nm (ꢀ/mol^-1dm³cm^-1): 431 (111806), 515 (7747), 551

5-(m-Iodoph en yl)-10,15,20-tr itolyl-21-m on oth iapor ph y-

r in (20). A solution of thiophene mono-ol 9 (0.5 g, 1.581 mmol),

p-tolylaldehyde (0.2 g, 0.2 mL, 1.581 mmol), and pyrrole (0.2

g, 0.2 mL, 2.372 mmol) were dissolved in 50 mL propionic acid

and refluxed for 3 h. Column chromatography of the crude

compound on silica gel using petroleum ether/dichloromethane

(80:20) gave compound 20 as violet solid in 2% yield (12 mg).

M. P. > 300 ° C. IR (neat, cm^-1) 3328 (NH), 3033, 2921, 2855,

(3145), 619 (1118), 677 (2791). Fluorescence: (λ_ex) 515 nm,

in toluene) λ_em/nm 682, 751 (sh), φ ) 0.0227.

5-(Octyloxyp h en yl)-10,15,20-tr i(p h en yl)- 21-m on oth ia -

p or p h yr in (17). A solution of thiophene mono-ol 4 (0.4 g,

1.256 mmol), benzaldehyde (0.1 g, 0.1 mL, 1.256 mmol), and

pyrrole (0.1 g, 0.1 mL, 1.884 mmol) in 50 mL propionic acid

was refluxed for 3 h. After standard workup, the crude

compound was purified by silica gel column chromatography

using petroleum ether/dichloromethane (80:20) and afforded

the desired N₃S porphyrin 17 as brown-violet solid in 4% yield

(40 mg). M. P. > 300 °C. IR (neat, cm^-1) 3335 (NH), 3059, 2933,

2861, 1249, 1177, 816, 709. ¹H NMR (300 MHz, CDCl₃, δ in

ppm) -2.68 (s, 1H), 0.93 (m, 3H), 1.25-1.48 (m, 8H), 1.61 (m,

2H), 1.96 (m, 2H), 4.22 (m, 2H), 7.32 (d, J ) 8.7 Hz, 2H), 7.75

(m, 9H), 8.18 (m, 6H), 8.25 (m, 2H), 8.59 (d, J ) 5.5 Hz, 2H),

8.69 (d d, 2H), 8.92 (s, 2H), 9.74 (d, J ) 5.2 Hz, 1H), 9.79 (d,

J ) 5.2 Hz, 1H). ¹³C NMR (75 MHz, CDCl₃): δ 14.2, 22.8, 26.3,

29.4, 29.6, 29.8, 31.9, 68.4, 113.7, 123.6, 123.8, 126.7, 127.6,

127.9, 128.9, 131.6, 133.2, 134.3, 134.5, 135.5, 138.9, 139.1,

141.1, 142.5, 147.3, 147.4, 154.3, 154.5, 157.3, 157.7, 159.3.

1

795, 729. H NMR (400 MHz, CDCl₃, δ in ppm) -2.69 (s, 1H),

2.68 (s, 9H), 7.50 (m, 6H), 7.59 (m, 2H), 8.09 (m, 8H), 8.64 (m,

3H), 8.69 (d, J ) 4.0 Hz, 1H), 8.95 (s, 2H), 9.68 (d, J ) 5.2 Hz,

1H), 9.77 (d, J ) 5.2 Hz, 1H). ¹³C NMR (100 MHz, CDCl₃): δ

21.5, 93.6, 124.1, 124.4, 127.4, 128.4, 128.8, 128.9, 129.1, 131.9,

132.6, 133.1, 133.4, 133.7, 134.2, 134.4, 134.7, 135.6, 135.8,

136.9, 137.2, 137.6, 138.1, 139.2, 139.3, 139.5, 139.6, 142.6,

143.3, 146.9, 147.1, 154.6, 154.7, 156.9, 157.7. ES-MS: C₄₇H₃₄N₃-

SI, calcd av mass 799.8, obsd m/z 800.0 (M⁺). Anal. calcd: C,

70.58; H, 4.27; N, 5.25; S, 4.01. Found: C, 70.27; H, 4.14; N,

5.20; S, 3.99. UV-vis λ_max/nm (ꢀ/mol^-1dm³cm^-1): 431 (345675),

549 (6665), 614 (2265), 618 (2751), 679 (4609). Fluorescence:

(λ_ex) 515 nm, in toluene) λ_em/nm 683, 750 (sh), φ ) 0.0155.

ES-MS:

C₅₂H₄₅N₃SO, calcd av mass 760.0, obsd m/z 760.2

5-(3-m et h yl-3-h yd r oxyb u t -1-yn -1yl)p h en yl-10,15,20-

Tr is (p-octyloxyp h en yl)- 21-m on ooxa p or p h yr in (21). The

furan mono-ol 10 (1.5 g, 5.853 mmol), p-octyloxybenzaldehyde

(1.5 g, 5.853 mmol) and pyrrole (0.6 g, 0.6 mL, 8.780 mmol)

(M⁺). Anal. calcd: C, 82.18; H, 5.97; N, 5.53; S, 4.22. Found:

C, 81.97; H, 5.92; N, 5.50; S, 4.18. UV-vis λ_max/nm (ꢀ/mol^-1

dm³cm^-1): 434 (196826), 517 (12227), 554 (5996), 621 (1615),

6808 J . Org. Chem., Vol. 69, No. 20, 2004

One-Flask Synthesis

were dissolved in 120 mL propionic acid and refluxed for 3 h.

The progress of the reaction was monitored with absorption

spectroscopy. After standard work up, the crude reaction

mixture was subjected to two clearly showed two spots

corresponds to the regular meso-tetrakis-(4-octyloxylphenyl)

N₄porphyrin and the desired N₃O porphyrin 21. The mixture

of two porphyrins was separated by column chromatography

on silica and the N₃O porphyrin 21 was collected as second

band using dichloromethane/ methanol (85:15) mixture. The

solvent was removed on rotary evaporator and afforded

compound 21 as green solid in 4% yield (120 mg). M. P. >300

° C. IR (neat, cm^-1) 3408 (NH), 2927, 2861, 1611, 1256, 1177,

gel using petroleum ether/dichloromethane (60:40) mixture

gave compound 24 as brown-violet solid in 3% yield (20 mg).

M. P. > 300 °C. IR (neat, cm^-1) 3335 (NH), 3105, 2927, 2855,

1

802, 709. H NMR (300 MHz, CDCl₃, δ in ppm) -2.68 (s, 1H),

2.71 (s, 3H), 7.49 (m, 2H), 7.57 (m, 1H), 7.63 (d, J ) 7.7 Hz,

2H), 7.85 (d, J ) 5.2 Hz, 2H), 7.94 (m, 4H), 8.13 (d, J ) 7.9

Hz, 2H), 8.69 (d, J ) 4.7 Hz, 1H), 8.77 (m, 2H), 8.89 (d, J )

4.4 Hz, 1H), 9.16 (s, 2H), 9.78 (d, J ) 5.2 Hz, 1H), 9.98 (d, J

) 5.2 Hz, 1H). ¹³C NMR (100 MHz, CDCl₃): δ 21.5, 29.7, 114.8,

115.1, 123.5, 125.9, 127.1, 127.9, 128.4, 128.8, 129.0, 129.1,

133.0, 133.4, 133.6, 134.0, 134.2, 134.4, 134.9, 135.2, 135.3,

137.7, 137.8, 139.9,140.1, 141.4, 143.1, 147.5, 148.7, 155.6,

155.8, 157.6, 157.9. ES-MS: C₃₉H₂₅N₃S₄, calcd av mass 663.9,

obsd m/z 664.1 (M⁺). Anal. calcd: C, 70.56; H, 3.80; N, 6.33;

S, 19.32. Found: C, 70.45; H, 3.68; N, 6.30; S, 19.21. UV-vis

1

815, 742. H NMR (300 MHz, CDCl₃, δ in ppm) 0.92 (m, 9H),

1.11-1.68 (m, 30H), 1.77 (s, 6H), 1.99 (m, 6H), 4.25 (t, 6H),

7.83 (t, 4H), 8.12 (m, 12H), 8.49 (t, 1H), 8.58 (d, J ) 4.8 Hz,

1H), 8.66 (t, 2H), 8.89 (s, 2H), 9.13 (d, J ) 5.1 Hz, 1H), 9.23

(d, J ) 4.8 Hz, 1H). ¹³C NMR (100 MHz, CDCl₃): δ 14.2, 22.8,

26.3, 27.3, 29.4, 29.4, 29.5, 31.5, 31.9, 65.6, 65.8, 68.6, 113.7,

114.2, 128.9, 129.5, 131.2, 131.9, 132.8, 134.2, 135.5, 138.2,

160.4, 160.5, 173.9, 174.2. ES-MS: C₇₃H₈₃N₃O₅, calcd. av. mass

1082.5, obsd. m/z 1082.9 (M⁺). Anal. Calcd.: C, 81.00; H, 7.73;

N, 3.88. Found: C, 79.83; H, 7.59; N, 3.55. UV-vis λ_max/nm

(ꢀ/mol^-1dm³cm^-1): 427 (101856), 512 (11939), 545 (6748), 615

(3599), 678 (3611). Fluorescence: (λ_ex) 515 nm, in toluene)

λ

_max/nm (ꢀ/mol^-1dm³cm^-1): 437 (239977), 521 (17583), 557

(7479), 624(2679), 687 (3244). Fluorescence: (λ_ex) 515 nm,

in toluene) λ_em/nm 699, 765 (sh), φ ) 0.0075.

5,10,15-Tr is -(4-p yr id yl)-20-p h en yl-21-m on ot h ia p or -

p h yr in (25). The samples of thiophene mono-ol 8 (0.4 g, 2.102

mmol), pyridyl-4-carboxaldehyde (0.2 g, 0.2 mL, 2.102 mmol),

and pyrrole (0.2 g, 0.2 mL, 3.153 mmol) were dissolved in 50

mL propionic acid and refluxed for 3 h. Column chromatog-

raphy of the crude compound on silica gel using dichlo-

romethane/methanol (94:6) mixture gave compound 25 as

λ_em/nm 684, 745 (sh), φ ) 0.0932.

1

5-(p-Eth yn ylp h en yl)-10,15,20-tr is (p-octyloxyp h en yl)-

violet solid in 7% yield (45 mg). H NMR (300 MHz, CDCl₃, δ

21-m on ooxa p or p h yr in (22). Compound 21 (0.1 g, 0.092

mmol) in dry benzene (40 mL) was treated with potassium

hydroxide (0.019 g, 0.139 mmol) in 15 mL methanol for 20 h

at 80° C. The completion of the reaction was judged by TLC.

The crude porphyrin 22 was purified by silica gel column

chromatography using dichloromethane/methanol (93:7) mix-

ture as green solid (43 mg, 41%). M. P. > 300 °C. IR (neat,

in ppm) -2.84 (s, 1H), 7.84 (m, 3H), 8.16 (m, 4H), 8.20 (m,

2H), 8.24 (m, 2H), 8.57 (d, J ) 4.7 Hz, 1H), 8.61 (d, J ) 4.7

Hz, 1H), 8.70 (d, J ) 4.6 Hz, 1H), 8.76 (d, J ) 4.4 Hz, 1H),

8.94 (d, J ) 1.9 Hz, 2H), 9.05 (m, 4H), 9.09 (m, 2H), 9.73 (d, J

) 5.5 Hz, 1H), 9.85 (d, J ) 5.5 Hz, 1H). ¹³C NMR (100 MHz,

CDCl₃): δ 21.5, 29.7, 126.9, 127.4, 128.3, 128.5, 128.9, 130.7,

131.7, 132.6, 132.8, 133.1, 133.6, 134.2, 134.4, 134.6, 135.5,

135.7, 137.6, 138.0, 139.1, 139.5, 141.8, 146.9, 148.3, 154.6,

156.8, 157.6. ES-MS: C₄₁H₂₆N₆S, Calcd av mass, 634.7, obsd

m/z 635.1 (M⁺). Anal. calcd: C, 77.58; H, 4.13; N, 13.24; S,

1

cm^-1) 3342 (NH), 2934, 2861, 1604, 1256, 1183, 815. H NMR

(400 MHz, CDCl₃, δ in ppm) 0.94 (m, 9H), 1.27-1.62 (m, 24H),

1.64 (t, 6H), 2.01 (t, 6H), 3.39 (s, 1H), 4.29 (t, 6H), 7.39 (br s,

6H), 7.97 (m, 2H), 8.29 (m, 8H), 8.69 (m, 4H), 8.83 (d, J ) 7.2

Hz, 2H), 9.36 (br s, 1H), 9.44 (br s, 1H). ¹³C NMR (100 MHz,

CDCl₃): δ 14.3, 22.9, 23.7, 26.4, 29.5, 29.6, 29.6, 29.8, 32.0,

68.6, 113.7, 114.2, 128.9, 130.0, 131.1, 131.8, 132.1, 133.2,

135.6, 137.2, 138.4, 142.9, 160.3, 160.5. ES-MS: C₇₀H₇₇N₃O₄,

calcd av mass 1023.5, obsd m/z 1024.3 (M⁺). Anal. calcd: C,

82.07; H, 7.58; N, 4.10. Found: C, 81.90; H, 7.49; N, 4.02. UV-

vis λ_max/nm (ꢀ/mol^-1dm³cm^-1): 426 (174996), 512 (13267), 546

(5293), 617 (2376), 678 (2844). Fluorescence: (λ_ex) 515 nm,

in toluene) λ_em/nm 684, 750 (sh), φ ) 0.1221.

5.05. Found: C, 77.26; H, 4.04; N, 13.02; S, 4.92. UV-vis λ_max

/

nm (ꢀ/mol^-1dm³cm^-1): 428 (155601), 512 (17086), 545 (6339),

616 (3626), 676 (4387). Fluorescence: (λ_ex) 515 nm, in toluene)

λ_em/nm 680, φ ) 0.0134.

5,10,15-Tr is-(3-p yr id yl)-20-p h en yl-21-m on oth ia p or p h y-

r in (26). Compound 8 (0.7 g, 3.678 mmol), pyridyl-3-carbox-

aldehyde (0.4 g, 0.3 mL, 3.678 mmol), and pyrrole (0.4 g, 0.4

mL, 5.517 mmol) were dissolved in 70 mL propionic acid and

refluxed for 3 h. The crude compound was purified by silica

gel column chromatography and the desired compound 26 was

collected in dichloromethane/methanol (94:6) mixture in 6%

5-(p-Iod op h en yl)-10,15,20-tr i(p-tolyl)-21-m on ooxa p or -

p h yr in (23). The samples of furan mono-ol 11 (4.8 g, 15.995

mmol), p-tolylaldehyde (1.9 g, 1.9 mL, 15.995 mmol), and

pyrrole (1.6 g, 1.7 mL, 23.993 mmol) were dissolved in 360

mL propionic acid and refluxed for 3 h. Column chromatog-

raphy of crude compound on silica gel in dichloromethane/

methanol (92:8) gave compound 23 in 2% yield (82 mg). M. P.

> 300 °C. IR (neat, cm^-1) 3427 (NH), 2921, 2848, 802, 729. ¹H

NMR (300 MHz, CDCl₃, δ in ppm) -1.55 (s, 1H), 2.69 (s, 9H),

7.54 (m, 6H), 7.85 (m, 2H), 8.10 (m, 8H), 8.49 (d, J ) 4.2 Hz,

2H), 8.55 (d, J ) 4.5 Hz, 1H), 8.63 (t, 2H), 8.89 (s, 1H), 9.14

(d, J ) 4.8 Hz, 1H), 9.19 (d, J ) 4.8 Hz, 1H). ¹³C NMR (75

MHz, CDCl₃): δ 14.2, 21.6, 22.6, 29.5, 29.8, 32.0, 94.6, 127.6,

127.8, 128.4, 134.4, 134.7, 236.1, 136.2, 137.4, 137.7, 138.0,

138.7, 139.0, 154.2, 154.8. ES-MS: C₄₇H₃₄N₃OI. calcd av mass

783.7, obsd m/z 784.4 (M⁺). Anal. calcd: C, 72.03; H, 4.37; N,

5.36. Found: C, 71.92; H, 4.29; N, 5.29. UV-vis λ_max/nm (ꢀ/

mol^-1dm³cm^-1): 423 (281708), 509 (23004), 540 (9297), 614

(4347), 673 (4401). Fluorescence: (λ_ex) 515 nm, in toluene)

yield as violet solid (68 mg). M. P. > 300 °C. IR (neat, cm^-1

)

1

3421 (NH), 2934, 2861, 802, 696. H NMR (400 MHz, CDCl₃,

δ in ppm) -2.74 (s, 1H), 7.79 (m. 7H), 8.24 (br s, 2H), 8.53 (m,

3H), 8.60 (d, J ) 4.4 Hz, 1H), 8.69 (d, J ) 4.4 Hz, 1H), 8.76 (d,

J ) 4.4 Hz, 1H), 8.94 (s, 2H), 9.04 (br s, 3H), 9.44 (m, 3H),

9.72 (d, J ) 5.2 Hz, 1H), 9.83 (d, J ) 5.2 Hz, 1H). ¹³C NMR

(100 MHz, CDCl₃): δ 29.7, 119.6, 119.8, 121.9, 122.8, 127.5,

127.7, 128.2, 128.8, 128.9, 132.8, 133.3, 134.1, 134.2, 135.2,

135.5, 135.6, 136.6, 138.0, 138.7, 138.9, 140.4, 140.8, 147.6,

147.8, 149.3, 153.4, 154.5, 157.2, 157.9. ES-MS: C₄₁H₂₆N₆S,

calcd av mass 634.7, obsd m/z 635.1 (M⁺). Anal. calcd: C, 77.58;

H, 4.13; N, 13.24; S, 5.05. Found: C, 76.89; H, 4.02; N, 13.05;

S, 4.94. UV-vis λ_max/nm (ꢀ/mol^-1dm³cm^-1): 430 (285065), 515

(23886), 548 (7299), 619 (3696), 679 (4689). Fluorescence: (λ_ex

) 515 nm, in toluene) λ_em/nm 683, 753 (sh), φ ) 0.0139.

5,10,15-Tr is (p -iod op h en yl)-20-(oct yloxyp h en yl)-21-

m on oth ia p or p h yr in (27). Samples of thiophene mono-ol 4

(1.0 g, 3.140 mmol), p-iodobenzaldehyde (0.7 g, 3.140 mmol),

and pyrrole (0.3 g, 0.3 mL, 4.710 mmol) were dissolved in 90

mL propionic acid and refluxed for 3 h. Column chromatog-

raphy of crude compound on silica gel in petroleum ether/

dichloromethane (80:20) mixture gave compound 27 as purple

solid in 3% yield (60 mg). M. P. > 300 °C. IR (neat, cm^-1) 3332

λ_em/nm 678, 746 (sh), φ ) 0.0171.

Tr ifu n ction a lized P or p h yr in Bu ild in g Block s. 5,10,-

15-Tr is(2-th ien yl)-20-(p-tolyl)-21-m on oth iapor ph yr in (24).

A solution of thiophene mono-ol 7 (0.4 g, 1.958 mmol),

2-thienylaldehyde (0.2 g, 0.2 mL, 1.958 mmol), and pyrrole (0.2

g, 0.2 mL, 2.937 mmol) in 50 mL propionic acid was refluxed

for 3 h. Column chromatography of crude compound on silica

1

(NH), 2934, 2861, 1485, 1249, 795, 703. H NMR (400 MHz,

CDCl₃, δ in ppm) -2.78 (s, 1H), 0.94 (m, 3H), 1.25-1.60 (m,

J . Org. Chem, Vol. 69, No. 20, 2004 6809

Gupta and Ravikanth

10H), 1.98 (m, 2H), 4.23 (m, 2H), 7.33 (d, J ) 7.6 Hz, 2H),

7.92 (m, 6H), 8.11 (m, 8H), 8.62 (t, 2H), 8.67 (d, J ) 4.4 Hz,

1H), 8.72 (d, J ) 4.4 Hz, 1H,), 8.92 (s, 2H), 9.70 (d, J ) 5.2

Hz, 1H), 9.79 (d, J ) 4.8 Hz, 1H). ¹³C NMR (100 MHz,

CDCl₃): δ 21.1, 53.5, 70.4, 71.9, 121.4, 124.0, 124.7, 126.3,

126.3, 126.5, 129.1, 129.4, 137.4, 140.3, 140.4, 146.2, 146.3,

Anal. calcd: C, 80.17; H, 6.62; N, 5.32; S, 1.74. Found: C,

80.64; H, 6.32; N, 5.57; S, 1.93. UV-vis λ_max/nm (ꢀ/mol^-1dm³

cm^-1): 424 (535799), 435 (510645), 518 (28439), 552 (34376),

588 (5762), 621 (3892), 683 (7256).

4-[(5,10,15-Tr im esityl-20-p or p h yr in a to) zin c(II)]-3′-[5,-

10,15-t r it o ly l-21-m o n o t h ia -20-p o r p h in y l]d ip h e n y l-

eth yn e (30). A solution of N₃S porphyrin 20 (12.0 mg, 15.0

µmol) and 5,10,15-tri(mesityl)-20-(4-ethynylphenyl) zinc por-

phyrin 35 (15.0 mg, 18.1 µmol) in dry toluene-triethylamine

(5:1, 15 mL) was purged with nitrogen for 10 min. The coupling

was initiated by adding AsPh₃(5.5 mg, 18.0 µmol) followed by

Pd₂(dba)₃(2.1 mg, 2.3 µmol) and the reaction mixture was then

stirred at 40 °C for 12 h. The excess AsPh₃and other impurities

were removed on silica gel column using petroleum ether/

dichloromethane (50:50) and the crude mixture of small

amounts of monomers and dimer were then separated using

neutral alumina column. The required dimer 30 was collected

with petroleum ether/dichloromethane (60:40) mixture as a

second band. The solvent was removed in a rotary evaporator

to afford dimer 30 in 58% yield (13.0 mg). Violet solid, M. P.

> 300 °C. IR (neat, cm^-1) 3322 (NH), 2940, 2661, 1736, 1604,

1453, 1006, 998, 808, 735. ¹H NMR (300 MHz, CDCl₃, δ in

ppm) -2.64 (s, 1H), 1.84 (s, 18H), 2.62 (s, 9H), 2.72 (s, 9H),

7.29 (m, 6H), 7.40 (t, 2H), 7.62 (m, 8H), 7.97 (m, 2H), 8.20 (m,

8H), 8.62 (m, 2H), 8.74 (m, 8H), 8.87 (m, 2H), 8.97 (s, 2H),

9.83 (m, 2H). ES-MS: C₁₀₂H₇₉N₇SZn, calcd av mass 1500.3,

obsd m/z 1500.9 (M⁺). UV-vis λ_max/nm (ꢀ/mol^-1dm³cm^-1): 424

(407869), 483 (4982), 515 (18868), 550 (19016), 591 (3241), 617

(2275), 677 (4201).

[5,10,15-Tr itolyl-21-m on oth ia -20-p or p h in yl]-4-[5,10,15-

t r ioct yloxyp h en yl-21-m on ot h ia -20-p or p h in yl]p h en yl-

eth yn e (31). A solution of N₃S porphyrin, 5-bromo-10,15,20-

tris(p-tolyl)-21-thiaporphyrin 36 (17.0 mg, 25.1 µmol), and N₃S

porphyrin 15 (26.1 mg, 25.1 µmol) in dry toluene (20 mL) was

purged with nitrogen for 10 min. To this solution were added

Pd₂(dba)₃(3.5 mg, 3.8 µmol), AsPh₃(9.4 mg, 30.1 µmol), and

Et₃N (8 mL). The resulting solution was then stirred at 40 °C

for 24 h. After this period, TLC analysis indicated the presence

of a new spot. The solution was concentrated in vacuo and the

resulting crude product was purified by neutral alumina

column chromatoghaphy. The expected compound 31 collected

in petroleum ether/dichloromethane (20:80), in 48% yield (20.0

mg). Violet solid, M. P. > 300 °C. IR (neat, cm^-1) 3421 (NH),

3348 (NH), 2934, 2861, 1525, 1459, 1249, 973, 815, 729.¹H

NMR (300 MHz, CDCl₃, δ in ppm) -2.59 (s, 1H), -2.10 s, 1H),

0.95 (m, 9H), 1.21-1.64 (m, 30H), 2.00 (m, 9H), 2.73 (m, 6H),

4.28 (m, 6H), 7.53 (m, 12H), 8.15 (m, 12H), 8.55 (m, 4H), 8.68

(m, 6H), 8.91 (m, 4H), 9.33 (br s, 1H), 9.39 (br s, 1H), 9.54 (d,

J ) 4.5 Hz, 1H), 9.93 (m, 2H), 10.52 (d, J ) 5.1 Hz, 1H). ES-

MS: C₁₁₁H₁₀₆N₆S₂O₃calcd av mass 1636.2, obsd m/z 1636.9

(M⁺). Anal. calcd: C, 81.48; H, 6.53; N, 5.14; S, 3.92. Found:

C, 81.02; H, 6.61; N, 5.56; S, 4.14. UV-vis λ_max/nm (ꢀ/mol^-1

dm³cm^-1): 439 (418923), 519 (43155), 578 (40541), 623 (7537),

688 (12499), 697 (12820).

148.6, 149.6, 149.8, 153.2. ES-MS:

C₅₂H₄₂N₃SOI₃, calcd av

mass 1137.7, obsd m/z 1137.9 (M⁺). Anal. calcd: C, 54.90; H,

3.72; N, 3.69; S, 2.82. Found: C, 53.88; H, 3.54; N, 3.41; S,

2.54. UV-vis λ_max/nm (ꢀ/mol^-1dm³cm^-1): 433 (384448), 516

(26574), 551 (11272), 620 (3850), 679 (8829). Fluorescence: (λ_ex

) 515 nm, in toluene) λ_em/nm 682, 745 nm (sh), φ ) 0.0066.

5,10,15-Tr is (4-p yr id yl)-20-( p-tolyl)-21-m on ooxa p or -

p h yr in (28). Condensation of the furan mono-ol 12 (2 g, 10.627

mmol), 4-pyridylcarboxaldehyde (1.1 g, 1.0 mL, 10.627 mmol),

and pyrrole (1.0 g, 1.1 mL, 15.941 mmol) in 220 mL propionic

acid at refluxing temperature for 3 h followed by column

chromatography of the crude compound on silica gel using

dichloromethane/methanol (86:14) gave compound 28 as green-

ish-violet solid in 2% yield (56 mg). M. P. > 300 °C. IR (neat,

cm^-1) 3414 (NH), 3046, 2927, 2855, 1591, 1472, 1407, 808, 736.

¹H NMR (400 MHz, CDCl₃, δ in ppm) 2.72 (s, 3H), 7.59 (d, J

) 7.6 Hz, 2H), 8.12 (m, 8H), 8.58 (m, 2H), 8.65 (m, 2H), 8.84

(m, 2H), 9.04 (m, 6H), 9.19 (br s, 1H), 9.34 (br s, 1H). ¹³C NMR

(100 MHz, CDCl₃): δ 14.1, 21.6, 22.7, 31.9, 52.9, 70.6, 119.0,

120.0, 121.2, 122.2, 127.9, 129.1, 129.3, 129.8, 134.32, 134.7,

136.3, 138.4, 148.3, 148.7, 149.6, 150.3, 150.6, 154.0, 155.3.

ES-MS: C₄₂H₂₈N₆O, calcd av mass 632.7, obsd m/z 633.2 (M⁺).

Anal. calcd: C, 79.73; H, 4.46; N, 13.28. Found: C, 79.62; H,

4.29; N, 13.05. UV-vis λ_max/nm (ꢀ/ mol^-1dm³cm^-1): 420

(95449), 506 (15025), 536 (6440), 611 (4063), 672 (3119).

Fluorescence: (λ_ex) 515 nm, in toluene) λ_em/nm 675, 743 (sh),

φ ) 0.0611.

Cova len t Dim er s. 4-[(5,10,15-Tr im esityl-20-p or p h yr i-

n a to) zin c(II)]-4′-[5,10,15-tr ioctyloxyph en yl-21-m on oth ia -

20-p or p h in yl]d ip h en yleth yn e (29). A solution of N₃S por-

phyrin 15 (15.0 mg, 14.4 µmol) and 5,10,15-tri(mesityl)-20-(4-

iodophenyl) zinc porphyrin 34 (16.0 mg, 17.3 µmol) were

dissolved in dry toluene-triethylamine (5:1, 18 mL) in a 25 mL-

round-bottomed flask. The flask was fitted with a reflux

condenser and a gas inlet tube was inserted through the top

of the condenser into the solution for argon purging. The

reaction vessel was placed in an oil bath preheated to 35 °C.

The nitrogen was purged for 15 min. To this solution, Pd₂-

(dba)₃(2.0 mg, 2.2 µmol) and AsPh₃(5.4 mg, 17.5 µmol) were

added and the reaction was stirred at 35 °C for 12 h. TLC

analysis of the reaction mixture indicated the virtual disap-

pearance of spots corresponding to starting materials and the

appearance of a new spot corresponding to dimer. The solvents

were removed in vacuo and the crude compound was passed

through a small silica column using petroleum ether/dichlo-

romethane (60:40) to remove the excess of AsPh₃, and the crude

mixture of small amounts of monomeric porphyrins along with

desired dimer was collected with petroleum ether/dichlo-

romethane (20:80). The Pd species remained bound to the top

of the column. The solution was concentrated in vacuo and

the resulting crude mixture of porphyrinic monomers and

dimer was dissolved in dichloromethane (3 mL) and dry slurry

was prepared by adding neutral alumina powder. The slurry

was loaded on neutral alumina column packed with petroleum

ether. The small amounts of porphyrinic monomers were

removed first with petroleum ether/dichloromethane and the

desired dimer 29 was collected with petroleum ether/dichlo-

romethane (20:80). Concentration of the solution gave por-

phyrin dimer as violet solid in 66% yield (12 mg). M. P. > 300

°C. IR (neat, cm^-1) 3335 (NH), 2934, 1611, 1505, 1453, 1236,

4-[(5,10,15-Tr im esityl-20-p or p h yr in a to) zin c(II)]-4′-[5,-

10,15-tr ioctyloxyphen yl-21-m on o oxa-20-por phin yl]diph en -

yleth yn e (32). A solution of N₃O porphyrin 22 (15.0 mg, 14.7

µmol) and 5,10,15-tri(mesityl)-20-(4-iodophenyl) zinc porphyrin

34 (17.9 mg, 17.5 µmol) in dry toluene-triethylamine (5:1, 15

mL) was purged with nitrogen for 10 min. To this solution,

AsPh₃(5.4 mg, 17.6 µmol) and Pd₂(dba)₃(2.0 mg, 2.2 µmol)

were added and stirred at 35 °C for 30 h. The solution was

concentrated in vacuo and the resulting crude product was first

subjected to silica gel column using petroleum ether/dichlo-

romethane (50:50) to remove excess AsPh₃and other impuri-

ties. The resultant crude compound was then subjected to

neutral alumina column chromatoghaphy and afforded the

dimer 32 using dichloromethane/methanol (99:1) in 37% yield

1

998, 821, 735. H NMR (300 MHz, CDCl₃, δ in ppm) -2.60 (s,

1 H), 0.86-0.99 (m, 15H), 1.25-1.66 (m, 24H), 1.87 (s, 18H),

1.99 (m, 6H), 2.64 (m, 9H), 4.25 (m, 6H), 7.32 (m, 12H), 8.12

(m, 10H), 8.32 (m, 4H), 8.72 (m, 8H), 8.79 (d, J ) 4.8 Hz, 2H),

8.93 (d, J ) 4.8 Hz, 2H), 8.98 (s, 2H), 9.81 (m, 2H). ES-MS:

as violet-green solid (10.0 mg). M. P. > 300 °C. IR (neat, cm^-1

)

3408 (NH), 2934, 2854, 1604, 1466, 1249, 998, 815, 729. ¹H

NMR (300 MHz, CDCl₃, δ in ppm) -2.54 (s, 1H), 0.83-0.95

(m, 21H), 1.25-1.74 (m, 18H), 1.86 (br s, 18H), 2.13 (m, 4H),

C

₁₂₃H₁₂₁N₇SO₃Zn, calcd av mass 1842.7, obsd m/z 1843.9 (M⁺).

6810 J . Org. Chem., Vol. 69, No. 20, 2004

One-Flask Synthesis

2.31 (m, 2H), 2.64 (m, 9H), 3.65 (br s, 2H), 4.27 (br s, 4H),

7.32 (m, 10H), 8.21 (m, 12H), 8.68 (m, 8H), 8.88 (m, 8H), 9.06

(d, J ) 4.2 Hz, 1H), 9.10 (d, J ) 5.1 Hz, 1H), 9.44 (m, 2H).

40) and the excess unreacted RuTPP(CO)(EtOH) was collected

as second band with petroleum ether/dichloromethane (50:50).

The tetramer 37 with small impurities was then subjected to

size exclusion chromatography using toluene and the pure

dimer 37 was collected as reddish-brown solid in 17% yield

(12 mg). M. P. > 300 °C. IR (neat, cm^-1) 3427 (NH), 2927, 2855,

1953, 1078, 1018, 1006, 998, 802, 716. ¹H NMR (300 MHz,

CDCl₃, δ in ppm) -4.33 (s, 1H), 1.78 (t, 4H), 1.86 (d, J ) 6.9

Hz, 2 H), 5.60 (d, J ) 6.6 Hz, 2H), 5.69 (d, J ) 6.6 Hz, 2H),

5.77 (d, J ) 6.6 Hz, 2H), 6.50 (d, J ) 4.5 Hz, 1H), 6.71 (d, J )

4.5 Hz, 1 H), 6.82 (m, 2H), 6.90 (m, 2H), 7.56-7.81 (m, 41H),

8.06 (m, 12H), 8.29 (m, 12H), 8.69 (m, 24H), 9.13 (d, J ) 5.4

Hz, 2H). ES-MS: C₁₇₆H₁₁₀N₁₈SO₃Ru₃, calcd av mass 2860.2,

obsd m/z 2861.2 (M⁺). Anal. calcd: C, 73.91; H, 3.88; N, 8.81;

S, 1.12. Found: C, 74.23; H, 4.11; N, 8.56; S, 1.16. UV-vis

ES-MS:

C₁₂₃H₁₂₁N₇O₄Zn, calcd av mass 1826.7, obsd m/z

1827.9 (M⁺). UV-vis λ_max/nm (ꢀ/mol^-1dm³cm^-1): 424 (386895),

514 (9826), 550 (19686), 607 (sh) (6129).

4-[5,10,15-Tr itolyl-21-m on o oxa -20-p or p h in yl]-4′-[5,10,-

15-tr ioctyloxyp h en yl-21-m on oth ia -20-p or p h in yl]d ip h en -

yleth yn e (33). Samples of N₃S porphyrin 15 (12.0 mg, 11.5

µmol) and N₃O porphyrin 23 (10.8 mg, 13.8 µmol) in dry

toluene (15 mL) was purged with nitrogen for 10 min. To this

solution were added Pd₂(dba)₃(1.6 mg, 1.7 µmol), AsPh₃(4.2

mg, 13.8 µmol), and Et₃N (5 mL). The resulting solution was

then stirred at 50 °C for 30 h. After this period, TLC analysis

indicated the presence of a new spot. The solution was

concentrated in vacuo and the resulting crude product was

purified by neutral alumina column chromatoghaphy. The

expected compound 33 collected as violet-green solid, in

dichloromethane/methanol (98:2) mixture, in 36% yield (7 mg).

M. P. > 300 °C. IR (neat, cm^-1) 3441 (NH), 3335 (NH), 2927,

2861, 1604, 1453, 1249, 1766, 985, 802. ¹H NMR (300 MHz,

CDCl₃, δ in ppm) -2.61 (s, 1H), 0.83-0.95 (m, 15H), 1.39-

1.68 (m, 24H), 1.95-2.02 (m, 6H), 2.76 (m, 6H), 3.66 (m, 3H),

4.20-4.28 (m, 6H), 7.29-7.39 (m, 8H), 7.51-7.65 (m, 8H),

7.68-7.78 (m, 8H), 8.09-8.20 (m, 8H), 8.35-8.38 (m, 4H),

8.48-8.55 (m, 4H), 8.64-8.85 (m, 4H), 8.87-9.03 (m, 2H), 9.81

(m, 2H). ES-MS: C₁₁₇H₁₁₀N₆SO₄, calcd av mass 1696.2, obsd

m/z 1696.6 (M⁺). UV-vis λmax/nm (ꢀ/mol^-1dm³cm^-1): 435

(211581), 517 (17327), 555 (11131), 619 (5262), 682 (4133).

Non cova len t Tetr a m er s. Un sym m etr ica l Non cova len t

Tetr a m er (37). The N₃S porphyrin 25 (15.0 mg, 0.024 mmol)

was dissolved in 20 mL of toluene in two-necked round-

bottomed flask and nitrogen was purged for 10 min. Ru TPP-

(CO)(EtOH) (64.6 mg, 0.082 mmol) was then added and the

solution was refluxed overnight. The color of the reaction

mixture changed from bright red to dark brownish red as the

reaction progressed. After 12 h, the TLC analysis showed the

virtual disappearance of starting porphyrins and the presence

of an additional spot corresponding to unsymmetrical porphy-

rin tetramer. The solvent was removed under reduced pressure

and the resulting crude compound was dissolved in a minimum

amount of dichloromethane and a dry slurry powder was

prepared by adding a small amount of silica gel followed by

the removal of the traces of solvent under reduced pressure.

The slurry was loaded on a silica gel column and eluted with

petroleum ether. The desired tetramer 37 was eluted as first

band and collected with petroleum ether/dichloromethane (60:

λ

_max/nm (ꢀ/mol^-1dm³cm^-1): 410 (740119), 434 (sh), 530

(48797), 564 (sh), 618 (3751), 680 (4472).

Un sym m etr ica l Non cova len t Tetr a m er (38). The reac-

tion of N₃S porphyrin 26 (23.0 mg, 0.036 mmol) and Ru TPP-

(CO)(EtOH) (97.1 mg, 0.123 mmol), in toluene (40 mL) under

the same reaction conditions as mentioned for compound 38

followed by chromatogarphic purification gave 38 in 20% yield

(21 mg). M. P. > 300 °C. IR (neat, cm^-1) 3440 (NH), 3065, 2934,

2855, 1953, 1078, 1018, 1006, 998, 802, 716. ¹H NMR (300

MHz, CDCl₃, δ in ppm) -3.90 (s, 1H), 1.99 (m, 6H), 5.46 (br s,

1H), 5.57 (br s, 1H), 5.73 (m, 2H), 5.99 (br s, 1H), 6.15 (br s,

1H), 6.59 (m, 2H), 6.77 (m, 2H), 6.92 (m, 2H), 7.25-7.96 (m,

53H), 8.16 (m, 12H), 8.53 (m, 24H,), 9.55 (br s, 1H), 9.68 (br s,

1H). ES-MS: C₁₇₆H₁₁₀N₁₈SO₃Ru₃, calcd av mass 2860.2, obsd

m/z 2861.2 (M⁺). UV-vis λ_max/nm (ꢀ/mol^-1dm³cm^-1): 411

(491530), 431 (sh), 531 (74966), 564 (sh), 621 (4619), 682

(5822).

Ack n ow led gm en t. This work was supported by a

grant from the Department of Atomic energy and

Department of Science and Technology and Council of

Scientific & Industrial Research, Govt. of India. NMR

and mass spectra were obtained at Department of

Chemistry, IIT-Bombay.

Su p p or tin g In for m a tion Ava ila ble: The characteriza-

tion data including ES-MS, ¹H NMR, ¹³C NMR, absorption,

and emission spectra of selected compounds. This material is

available free of charge via the Internet at http://pubs.acs.org.

J O040178U

J . Org. Chem, Vol. 69, No. 20, 2004 6811

Article Doi

One-flask synthesis of mono- and trifunctionalized 21-thia and 21-oxaporphyrin building blocks and their application in the synthesis of covalent and noncovalent unsymmetrical porphyrin arrays

DOI: 10.1021/jo040178u

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Full text of DOI:10.1021/jo040178u

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