P(RNCH2CH2)3N-catalyzed 1,2-addition reactions of activated allylic synthons

Article abstract of DOI:10.1021/jo0106492

Activated allylic compounds of the type RCH:CHCH₂Z (Z = CN, CO₂Me) react efficiently with aromatic aldehydes in the presence of 20-40 mol % of P(R′NCH₂CH₂)₃N at -94 to -63 °C. Both R = H and R = Me le

Full text of DOI:10.1021/jo0106492

426
J . Org. Chem. 2002, 67, 426-430
P (RNCH2CH2)3N-Ca ta lyzed 1,2-Ad d ition Rea ction s of Activa ted
Allylic Syn th on s
Philip B. Kisanga† and J ohn G. Verkade*,‡
Department of Chemistry, Iowa State University, Ames, Iowa 50010
jverkade@iastate.edu
Received J une 25, 2001
Activated allylic compounds of the type RCH:CHCH2Z (Z ) CN, CO2Me) react efficiently with
aromatic aldehydes in the presence of 20-40 mol % of P(R′NCH2CH2)3N at -94 to -63 °C. Both R
) H and R ) Me lead exclusively to R-addition products. When R ) H and Z ) CN, an allylic
transposition occurs to afford a Baylis-Hillman product as the only product.
In tr od u ction
place the negative charge in both the R and γ positions,6
it is not uncommon to observe both R- and γ-alkylation
products in reactions of such ambident anions.6 γ-Addi-
tion of allylic anions has been traditionally achieved via
the use of Grignard reagents of the type RCH:CHCH2-
MgX.7 Since Grignard reagents attack carbonyl groups,
the use of carbonyl-functionalized Grignard reagents is
therefore not possible. This is also true for allyl barium
reagents commonly used for R-addition of allylic anions
to carbonyl compounds.8 Hence, commonly used func-
tionalized allylic anions employed for C-C bond forma-
tion are those that possess heteroatoms such as silicon,
oxygen, sulfur, nitrogen, or a halogen.6 Allylic anions
stabilized by a strong electron withdrawing group, such
as SO, SO2, or P(O)R2, have also been utilized.6 However,
it should be noted that substrates bearing these func-
tionalities are less prone to nucleophilic addition reac-
tions at the activating group and are employed to a lesser
extent in organic synthesis than substrates containing
nitrile9 or ester10 functionalities.
The formation of C-C bonds is of significant utility in
organic synthesis for facilitating the assembly of building
blocks into larger molecules.1 Among organic transforma-
tions that proceed through C-C bond formations are
reactions such as aldol condensation,2 the Henry reac-
tion,3 Knoevenagel condensation4 and the Baylis-
Hillman reaction,5 all of which (except the Baylis-
Hillman reaction) proceed through the addition of anions
derived from compounds bearing an activating (electron
withdrawing) group and/or a halogen. Stabilized allylic
anions have also been used for the construction of C-C
bonds.6 Since the resonance forms of the allylic anion
† Present address: Syracuse Research Center, Albany Molecular
Research, Inc., 7001 Performance Drive, North Syracuse, NY 13212.
‡ Phone: (515) 294-5023. Fax: (515) 294-0105.
(1) For recent literature, see: (a) Kamimura, A.; Mitsudera, H.;
Asano, S.; Kidera, S.; Kakehi, A. J . Org. Chem. 1999, 64, 6353. (b)
Kobayashi, S.; Nagayama, S.; Busujima, T. Tetrahedron 1999, 55, 8739.
(c) Denmark, S. E.; Su, X. Tetrahedron 1999, 55, 8727. (d) Kanemasa,
S.; Araki, T.; Kanai, T.; Wada, E. Tetrahedron Lett. 1999, 40, 5059.
For reviews, see: (e) Mahrwald, R. Chem. Rev. 1999, 99, 1095. (f) Bach,
T. Angew. Chem., Int. Ed. Engl. 1994, 33, 417.
(2) (a) Rosini, G. In Comprehensive Organic Synthesis, Vol. 2; Trost,
B. M., Ed.; Pergamon: New York, 1991; pp 321-340. (b) For recent
publications on the utility of the Henry reaction, see: Iseki, K.; Oishi,
S.; Sasai, H.; Shibasaki, M. Tetrahedron Lett. 1996, 37, 9081. Barco,
A.; Benetti, S.; Risi, C.; Polloni, G. Tetrahedron Lett. 1996, 37, 7599.
Sasai, H.; Hiroi, M.; Yamada, Y.; Shibasaki, M. Tetrahedron Lett. 1997,
38, 6031. Shibasaki, M.; Sasai, H.; Arai, T. Angew. Chem., Int. Ed.
Engl. 1997, 36, 1236.
Subsequent to the synthesis of bases of type 1 first
synthesized in our laboratories,11 we have found that
these compounds act as superior catalysts and reagents
for a variety of reactions. For example, we have used
(3) For recent literature, see: (a) Florio, S.; Troisi, L.; Capriati, V.;
Coletta, G. Tetrahedron 1999, 55, 9859. (b) Paquette, L. A.; Kern, B.
E.; Mendez-Andino, J . Tetrahedron Lett. 1999, 40, 4129. (c) Heravi,
M. M.; Tajbaksh, M.; Mohajerani, B.; Ghassemzadeh, M. Z. Natur-
forsch., B: Chem. Sci. 1999, 54, 541. (d) Rodriguez, I.; Sastre, G.;
Corma, A.; Iborra, S. J . Catal. 1999, 183, 14. For reviews, see: (e)
Lorsbach, B. A.; Kurth, M. Chem. Rev. 1999, 99, 1549. (f) J ones, G.
Org. React. 1999, 15, 204.
them successfully for the synthesis of â-nitroalkanols,12
â-hydroxy nitriles,13 silylated alcohols,14 glutaronitriles,15
(4) For recent literature, see: (a) Akhmetvaleev, R. R.; Imaeva, L.
R.; Belogaeva, T. A.; Baikova, I. P.; Miftakhov, M. S. Russ. J . Org.
Chem. 1999, 35, 242. (b) Fukuzawa, S.; Tatsuzawa, M.; Hirano, K.
Tetrahedron Lett. 1998, 39, 6899. (c) Inoue, S.; Ibawuchi, Y.; Irie, H.;
Hatakeyama, S. Synlett 1998, 7, 735. For reviews, see: (d) Furstner,
A. Organozinc Reagents 1999, 287. (e) Inanaga, J . Trends Org. Chem.
1990, 1, 23.
(5) For recent reviews and pertinent references, see: (a) Basavaiah,
D.; Rao, P. D.; Hyma, R. S. Tetrahedron 1996, 52, 8001. (b) Drewes, S.
E.; Roos, G. H. P. Tetrahedron 1988, 44, 4653. (c) Langer, P. Angew.
Chem., Int. Ed. 2000, 39, 3049.
(7) Richey, H. G., J r.; Benson, R. M. J . Org. Chem. 1980, 45, 5036.
(8) (a) Yasue, K.; Yanagisawa, A.; Yamamoto, H. Bull. Chem. Soc.
J pn. 1997, 70, 493. (b) Yasue, K.; Habua, S.; Yasue, K.; Yamamoto,
H. J . Am. Chem. Soc. 1994, 116, 6130.
(9) For recent reviews, see: (a) Gridnev, I. D.; Gridneva, N. A. Usp.
Khim. 1995, 64, 1095; Chem. Abstr. 1996, 124, 288342. (b) Michel, R.
A.; Mozzon, M.; Berta, R. Coord. Chem. Rev. 1996, 147, 299.
(10) For recent reviews, see: (a) Spillane, W. J . Org. React. Mech.
1996, 19. (b) Wladislaw, B.; Marzorati, L.; Di Vitta, C. Main Group
Chem. News 1996, 4, 18.
(6) For recent reviews, see: (a) Katritzky, A. R.; Piffl, M.; Lang, H.;
Anders, E. Chem. Rev. 1999, 99, 665. (b) Katritzky, A. R.; J iang, J . J .
Prakt. Chem. 1999, 341, 79. (c) Krafft, M. E.; Fu, Z.; Procer, M. J .;
Wilson, A. M.; Dasse, O. A.; Hirosawa, C. Pure Appl. Chem. 1998, 70,
1083.
(11) (a) Schmidt, H.; Lensink, C.; Xi, S. K.; Verkade, J . G. Z. Anorg.
Allg. Chem. 1989, 578, 75. (b) Laramay, M. A. H.; Verkade, J . G. Z.
Anorg. Allg. Chem. 1991, 605, 163. (c) Wroblewski, A.; Pinkas, J .;
Verkade, J . G. Main Group Chem. 1995, 1, 69. (d) Kisanga, P.; Verkade,
J . G. Tetrahedron 2001, 57, 467.
10.1021/jo0106492 CCC: $22.00 © 2002 American Chemical Society
Published on Web 12/27/2001

P(RNCH2CH2)3N-Catalyzed Reactions of Allylic Synthons
Sch em e 1
J . Org. Chem., Vol. 67, No. 2, 2002 427
oxazolines,,16 a novel ylide,17 R,â-unsaturated nitriles,18
and homoallylic alcohols.19These nonionic bases have also
been used successfully in the promotion of Michael
addition reactions,20 oxa-Michael addition reactions,20
Knoevenagel condensations,21 and Wittig olefination
reactions.22 We previously reported that â,γ-unsaturated
nitriles undergo dimerization reactions to afford glu-
taronitriles as the only products.15 We postulated a
mechanism for that reaction in which we assumed that
the pathway involves the formation of an allylic anion
that either deprotonates the protonated base to form an
R,â-unsaturated nitrile or undergoes a Michael-type
addition to an already formed R,â-unsaturated nitrile
(Scheme 1). Scheme 1 suggests that the resonant allylic
anions 3a and 3b are sufficiently stable to persist in the
reaction mixture until they add to an R,â-unsaturated
nitrile molecule. Although we have recently been able to
utilize bases of type 1 for the isomerization of methylene-
interrupted double bonds23 (a process that involves the
formation of allylic anions), and for the dimerization of
allylic cyanides,15 all our attempts to utilize anions of type
3 in other syntheses have heretofore failed.
As a continuation of our previous work on glutaro-
nitrile synthesis,15 we report here the first proazaphos-
phatrane-catalyzed reaction of activated allylic com-
pounds to produce either a Baylis-Hillman product or a
â,γ-unsaturated 1,2-addition product, depending on the
type of allylic compound employed. To our knowledge,
there have been only a few reports in which allylic
cyanides and esters of the type used here have been
utilized in 1,2-addition to aldehydes.24 The authors of one
of the reports achieved such a reaction in the presence
of cadmium chloride and obtained a mixture of R- and
γ-addition products,24a which contrasts our observations
in which exclusive R-addition is encountered. The other
reactions were achieved using a variety of lithium bases
such as PhSLi,24b LDA,24c,e or t-BuLi24d or other alkali
metal bases such as NaHMDS24c or KHMDS.24c
Resu lts a n d Discu ssion
Attempted reaction of allyl cyanide with benzaldehyde
at room temperature in the presence of 10-20 mol % of
1a or 1b consistently produced in our hands the corre-
sponding glutaronitrile as the only product.15 We also
observed no evidence for the reaction of allyl cyanide with
benzaldehyde in the presence of 20 mol % of either 1a or
1b in THF upon reducing the temperature to -20 °C,
although an undetermined amount of the corresponding
glutaronitrile15 was observed. However, in the presence
of 20 mol % of 1a in THF and by reducing the temper-
ature to -63 °C, we were able to observe the formation
of the corresponding Baylis-Hillman product in 32%
conversion as shown by 1H NMR analysis of the reaction
mixture. Increasing the amount of this base to 30 mol %
led to an increase in the conversion to the Baylis-
Hillman product to about 64% under the same conditions.
With 40 mol % of 1b, complete conversion was observed
and an 88% isolated yield of the Baylis-Hillman product
7a was realized. Reactions employing 1a or 1c afforded
inconsistent but low conversions, and therefore only 1b
was henceforth used in this study. Interestingly, the
Baylis-Hillman product we observe stems from allylic
transposition. It is worth comparing this result to that
recently reported by Yamamoto and co-workers in which
R,â-unsaturated esters were deprotonated by lithium
2,2,6,6-tetramethylpiperidide (LTMP), followed by treat-
ment with a carbonyl substrate in the presence of
aluminum tris(2,6-diphenylphenoxide) (ATPH) to afford
a γ-addition product with retention of both the position
and geometry of the double bond.25
The Baylis-Hillman reaction has been of interest to
researchers for decades.26 Generally, high pressure is
required to induce this reaction between an R,â-unsatu-
(12) Kisanga, P.; Verkade, J . G. J . Org. Chem. 1999, 64, 4298.
(13) Kisanga, P.; McLeod, D.; D′Sa, B.; Verkade, J . G. J . Org. Chem.
1999, 64, 3090.
(14) D’Sa, B.; Verkade, J . G. J . Org. Chem. 1996, 61, 2963.
(15) Kisanga, P.; D′Sa, B.; Verkade, J . G. J . Org. Chem. 1998, 63,
10057.
(16) Kisanga, P.; Ilankumaran, P.; Verkade, J . G. Tetrahedron Lett.
2001, 43, 6263.
(17) Wang, Z., Verkade, J . G. Tetrahedron Lett. 1998, 39, 9331.
(18) D’Sa, B.; Kisanga, P.; Verkade, J . G. J . Org. Chem. 1998, 63,
3691.
(24) (a) Bo, L.; Fallis, A. G. Tetrahedron Lett. 1986, 27, 5193. (b)
Ono, M.; Nishimura, K.; Nagaoka, Y.; Tomioka, K. Tetrahedron Lett.
1999, 40, 1509. (c) Ruano, J . L. G.; Fernandez, I.; Catalina, M. P.;
Hermoso, J . A.; Sanz-Aparicio, J .; Martinez-Ripoll, M. J . Org. Chem.
1998, 63, 7157. (d) Takahashi, T.; Tomida, S.; Doi, T. Synlett 1999 5,
644. (e) Chesney, A.; Marko, I. E. Synth. Commun. 1990, 20, 3167.
(25) Saito, S.; Shiozawa, M.; Yamamoto, H. Angew. Chem., Int. Ed.
1999, 38, 1769.
(19) Wang, Z.; Kisanga, P.; Verkade, J . G. J . Org. Chem. 1999, 64,
6459.
(20) Kisanga, P.; Ilankumaran, P.; Verkade, J . G. Manuscript in
preparation.
(21) McLaughlin, P.; Kisanga, P.; Verkade, J . G. Manuscript in
preparation.
(22) Wang, Z.; Verkade, J . G. Heteroatom Chem. 1998, 9, 687.
(23) D’Sa, B.; Kisanga, P.; Yu, Z.; Verkade, J . G. Manuscript in
preparation.
(26) For recent references, see: (a) Iwama, T.; Kinoshita, H.;
Kataoka, T. Tetrahedron Lett. 1999, 40, 3741. (b) Evans, M. D.; Kaye,
P. T. Synth. Commun. 1999, 29, 2137. (c) Sugahara, T.; Ogasawara,
K. Synlett 1999, 4, 419. (d) Ramachandran, P. V.; Reddy, M. V. R.;
Rudd, M. T.; De Alaniz, J . R. Tetrahedron Lett. 1998, 39, 8791. (e)
Kamimura, A.; Gunjigake, Y.; Mitsuder, H.; Yokoyama, S. Tetrahedron
Lett. 1998, 39, 7323.

428 J . Org. Chem., Vol. 67, No. 2, 2002
Ta ble 1. Rea ction s of Allylic Com p ou n d s w ith Ald eh yd es
Kisanga and Verkade
Sch em e 2
phatrane (Scheme 3). The allylic anion thus produced
could add to the aldehyde to afford an intermediate
alkoxide anion which is sufficiently basic to deprotonate
allyl cyanide, thus possibly facilitating a catalytic reac-
tion. However, it seems more likely that the alkoxide
undergoes a facile 1,3-proton shift, giving a terminal
carbanion that deprotonates either allyl cyanide or the
protonated base 1H+ with resultant regeneration of the
prozazphosphatrane base that then re-enters the cata-
lytic cycle in Scheme 3. This mechanism is supported by
rated compound and a carbonyl compound in the pres-
ence of an amine such as DABCO, and lengthy periods
of time (1-4 weeks) are usually required.27 The reaction
shown in Scheme 2 affords this product under very mild
conditions and very short reaction times. Furthermore,
this reaction is successful with aromatic aldehydes that
have generally led to unreliable results under typical
Baylis-Hillman conditions.28 Unlike the nucleophilic
pathway that has been proposed for traditional Baylis-
Hillman reactions,27 the reaction shown in Scheme 2 is
proposed to proceed through an allylic anion produced
by the deprotonation of allyl cyanide by the proazaphos-
the observation that a reaction mixture monitored by 31
P
NMR spectroscopy at -50 °C revealed the existence of
both the free base and its protonated form 1bH+. This
observation is in accord with our previous study showing
that a reaction mixture containing 6a and 1b in CD3CN
at room temperature contained both the free base and
its protonated form in addition to deuterium scram-
bling.15
Since several Baylis-Hillman adducts and their de-
rivatives have recently been found to be efficient anti-
malarial agents,29 our protocol offers an easy route to a
variety of Baylis-Hillman adducts that could be screened
for antimalarial activity. Our methodology is character-
ized by faster rates compared with the most recently
(27) (a) Basaviah, D.; Krishnamacharyulu, M.; Hyma, R. S.; Sarma,
P. K. S.; Kumaragurubaran, N. J . Org. Chem. 1999, 64, 1197. (b) van
Rozendaal, E. L. M.; Voss, B. M. W.; Scheeren, H. W. Tetrahedron 1993,
49, 6931.
(28) Brzezinski, L. J .; Rafel, S.; Leahy, J . W. J . Am. Chem. Soc. 1997,
119, 4317.
(29) Kundu, M. K.; Sundar, N.; Kumar, S. K.; Bhat, S. V.; Biswas,
S.; Valecha, N. Bioorg. Med. Chem. Lett. 1999, 9, 731.

P(RNCH2CH2)3N-Catalyzed Reactions of Allylic Synthons
Sch em e 3
J . Org. Chem., Vol. 67, No. 2, 2002 429
Sch em e 4
Sch em e 5
reported variations of the Baylis-Hillman reaction, such
as a DABCO-catalyzed reaction in the presence of LiClO4
(20-48 h, 0 to -25 °C, 35-85% yield),30 a chalcogeno-
Baylis-Hillman reaction that requires a 2-fold excess of
the R,â-unsaturated compound in addition to 1.5 equiv
of DBU, or 2 equiv of Et2NH to which is also added other
reagents such as Me2S or Ti(O-i-Pr)4.31 Our reaction was
equally successful with p-chlorobenzaldehyde, affording
the corresponding Baylis-Hillman product 7b in 93%
yield (Table 1). However, aliphatic aldehydes such as
pivalaldehyde and n-butyraldehyde led only to compli-
cated reaction mixtures which upon workup were ob-
served to contain small amounts of unreacted aldehydes
and unidentified substances.The higher homologue of
allyl cyanide, namely, (E)-pentenenitrile (6b) also under-
went an R-addition reaction under similar conditions to
afford the novel unsaturated â-hydroxy nitrile 7c shown
in Scheme 4 and Table 1. The assumption that an allylic
anion is also formed in this reaction is justified by 31P
NMR observations on this reaction made in experiments
analogous to those described above. We observe no
detectable amounts of γ-addition products in our reac-
tions. The reactions of p-chlorobenzaldehyde and of
p-fluorobenzaldehyde with 6b followed a similar course,
affording the corresponding â-hydroxy â′,γ′-unsaturated
nitriles 7d and 7e in 87% and 91% yields, respectively
(Table 1). Noteworthy here is the formation of a highly
functionalized system in a single step. Reactions of allylic
anions reported in the literature are generally devoid of
selectivity and usually give rise to a mixture of the R-
and γ-addition products.6
Compounds analogous to 7c (e.g., 7i discussed below)
have been prepared by others through a multistep
procedure that utilizes aluminum turnings, mercuric
chloride, and sulfur-containing intermediate compounds.32
Another method for preparing these compounds is to
react an R,â-unsaturated ester with carbonyl compounds
in the presence of LDA and HMPA (a well-known
carcinogen).33 The unsaturated alcohol products (e.g., 7c-
7l in Table 1) are useful intermediates for the synthesis
of substituted tetrahydrofurans through base-promoted
electrophilic cyclizations.33,34 The formation of 7c-7l (as
a 1:1 mixture of diastereomers) is assumed to originate
from polarization of the double bond by the methyl group,
a process that places a partial negative charge adjacent
to an anionic carbon, thus favoring a 1,3-proton shift and
the subsequent deprotonation reaction shown in Scheme
4.
This result was sufficiently intriguing that we decided
to explore its extension to other activated allylic com-
pounds. Thus, methyl 3-butenoate reacted with benz-
aldehyde under the conditions shown in Scheme 5 to
(32) Galatsis, P.; Millan, S. D.; Nechala, P.; Fergusson, G. J . Org.
Chem. 1994, 59, 6643.
(33) Brownbridge, P.; Durman, J .; Hunt, P. G.; Warren, S. J . Chem.
Soc., Perkin. Trans. 1 1986, 1947.
(34) Tiecco, M.; Testaferri, L.; Tingoli, M.; Bagnoli, L.; Marini, F.
Gazz. Chim. Ital. 1996, 126, 635.
(30) Kawamura, M.; Kobayashi, S. Tetrahedron Lett. 1999, 40, 1539.
(31) Kataoka, T.; Iwama, T.; Kinoshita, H.; Tsujiyama, S.; Tsuru-
kami, Y.; Iwamura, T.; Watanabe, S. Synlett 1999, 2, 197.

430 J . Org. Chem., Vol. 67, No. 2, 2002
Kisanga and Verkade
afford an unsaturated ester, 8, arising from R-addition
followed by dehydration. However, this product proved
to be unstable and underwent further transformations
to unidentified products. Upon reducing the amount of
base to 20 mol %, unsaturated aldol products 7f, (Scheme
5) 7g, and 7h (Table 1) were isolated upon reacting 6c
with benzaldehyde, 4-fluorobenzaldehyde, and 4-chloro-
benzaldehyde, respectively. All attempts to form the
corresponding Baylis-Hillman product 9 were fruitless.
However, by using 30 mol % of 1b and by carrying out
the reaction of PhCHO with 6c for 6 h at -78 °C, a (7:
3:2) mixture of three products i.e., 7f, 8, and the desired
Baylis-Hillman product 9 was observed upon analyzing
the reaction mixture by 1H NMR spectral integration.
bluish complex in the presence of bases of type 1.14,19 This
result may also be associated with nucleophilic attack
on the nitro group which interrupts the course of the
reaction. The relatively lower reactivities of p-chloro-
benzaldehyde and p-fluorobenzaldehyde relative to benz-
aldehyde are also consistent with observations made on
other reactions promoted by bases of type 1 which we
reported previously.13,19 However, the origin of this result
is not clear at this point.
Exp er im en ta l Section
All reactions were conducted under nitrogen. The aldehydes
and allylic compounds were used as received without further
purification. The bases were prepared according to our previ-
ously reported procedures.11
Gen er a l P r oced u r e for th e Rea ction of Allylic Com -
p ou n d s w ith Ald eh yd es. Nitrogen was admitted to a small
evacuated flask and then 2.00 mL of dry THF was added
followed by 2.00 mmol of the allylic substrate. The reaction
mixture was then stirred at the required temperature (Table
1) for 10 min. A solution of proazaphosphatrane base 1b (Table
1) in 2 mL of THF was added dropwise over 5 min and the
resulting solution was stirred for an additional 5 min. This
was followed by the dropwise addition of a solution of 2.0 mmol
of the aldehyde in 0.75 mL (2 mL in the case of 5b) of dry
THF over a period of 2-3 min. The reaction mixture was then
stirred for the time periods specified in Table 1, at the end of
which time the mixture was quenched by the addition of 1 mL
of MeOH followed by stirring for 5 min. The crude mixture
was immediately loaded onto a small silica gel column and
flashed off with 5% MeOH in ether. The volatiles were removed
under vacuum and the crude product was fractionated on a
silica gel column with 60-75% ether in hexane. None of the
product diastereomers could be separated by column chroma-
tography except for those of the â-hydroxy esters 7i-7k .
Neither of the diastereomers of 7f could be separated
from the reaction mixture, because 9 and both diaster-
eomers of 7f always eluted together. The reactions of 6c
with aliphatic aldehydes (pivalaldehyde, n-butyralde-
hyde, and isobutyraldehyde) were not successful under
the above conditions. Only complicated reaction mixtures
containing some unreacted starting aldehyde and un-
identified material(s) were observed in all three cases.
Reactions employing the higher homologue methyl trans-
3-pentenoate (6d ) afforded only an incomplete reaction
in the presence of 20 mol % of 1a . In the presence of 40
mol % of 1b, the reactions of each of the arylaldehydes
benzaldehyde, 4-chlorobenzaldehyde, 4-fluorobenzalde-
hyde, and acetaldehyde with 6d afforded the correspond-
ing â-hydroxy unsaturated esters 7i, 7j,7k , and 7l in high
yields (Table 1). The reaction of benzaldehyde with
phenyl allyl sulfone gave the R-adduct 7m with no allylic
transposition to the corresponding Baylis-Hillman prod-
uct. The inability of p-nitrobenzaldehyde to react under
our conditions to give 7n in Table 1 while disappointing
is in accord with previous reports from our laboratories
in which this substrate had been found to form a green-
Ack n ow led gm en t. We thank the donors of the
Petroleum Research Fund, administered by the Ameri-
can Chemical Society, and the National Science Foun-
dation for grant support of this research.
Su p p or t in g In for m a t ion Ava ila b le: 1H and 13C NMR
spectral data for the products reported. This material is
available free of charge on the Internet at http://pubs.acs.org.
J O0106492