Synthesis of (4Z)-1,1-diphenyl-1,2,4-heptatrien-6-ynes and their facile cycloaromatizations to α,3-didehydrotoluene biradicals having a triarylmethyl radical center

Article abstract of DOI:10.1021/jo961073x

The Horner reaction between enynyl aldehydes 12 and phosphinoxy carbanion 11 provided enyneallenes 14. Thermolysis (37-80°C) of 1,4-cyclohexadiene solutions of 14 gave 20 via α,3-didehydrotoluene biradicals 19 having a reactive aryl radical center and a stabilized triarylmethyl radical center. In the absence of 1,4-cyclohexadiene, 19e underwent intramolecular H-atom transfer between the proximal benzylic methyl group and the aryl radical center to give the more stable biradical 21, the ultimate precursor of 22.

Full text of DOI:10.1021/jo961073x

J . Org. Chem. 1996, 61, 8503-8507
8503
Syn th esis of (4Z)-1,1-Dip h en yl-1,2,4-h ep ta tr ien -6-yn es a n d Th eir
F a cile Cycloa r om a tiza tion s to r,3-Did eh yd r otolu en e Bir a d ica ls
Ha vin g a Tr ia r ylm eth yl Ra d ica l Cen ter
Bin Liu, Kung K. Wang,* and J effrey L. Petersen†
Department of Chemistry, West Virginia University, Morgantown, West Virginia 26506
Received J une 7, 1996X
The Horner reaction between enynyl aldehydes 12 and phosphinoxy carbanion 11 provided enyne-
allenes 14. Thermolysis (37-80 °C) of 1,4-cyclohexadiene solutions of 14 gave 20 via R,3-
didehydrotoluene biradicals 19 having a reactive aryl radical center and a stabilized triarylmethyl
radical center. In the absence of 1,4-cyclohexadiene, 19e underwent intramolecular H-atom transfer
between the proximal benzylic methyl group and the aryl radical center to give the more stable
biradical 21, the ultimate precursor of 22.
Sch em e 1
In tr od u ction
The Myers cyclization of (Z)-1,2,4-heptatrien-6-ynes
(enyne-allenes) to R,3-didehydrotoluene biradicals occurs
under mild thermal conditions (eq 1).1 The resulting R,3-
didehydrotoluene biradicals contain a highly reactive aryl
radical center and a stabilized benzylic radical center.
While there is little chance of producing a persistent aryl
radical because H-atom abstraction generates a strong
aryl C-H bond, the benzylic radical center could become
persistent or even stable2 if proper substituents are
placed at the terminus of the allenic end of 1.
Sch em e 2
We recently reported that enyne-allene 3 undergoes
a facile Myers cyclization reaction in the presence of 1,4-
cyclohexadiene (1,4-CHD) to furnish 5 in 58% yield
(Scheme 1).3 The reaction presumably proceeds through
biradical 4 having an R,R-di-tert-butylbenzylic radical
center, which was reported to be persistent in dilute
solution at rt for several days.4 It is worth noting that
the presence of two sterically demanding tert-butyl
groups in 3 does not significantly affect the rate of
cycloaromatization when compared to that of 1. Presum-
ably, the small size of the hydrogen atom at the acetylenic
terminus minimizes the steric interactions even with the
tert-butyl group, and the formation of a more stable
tertiary benzylic radical in 4 partially compensates for
the increased steric interactions.
In a recent report by Shibuya and co-workers, the
enediyne 6 was treated with trifluoroacetic acid in the
presence of 1,4-CHD at 25 °C to form 9 (85% yield) in 2
h (Scheme 2).5 The reaction was proposed to proceed
through an initial acid-catalyzed reaction to form the s-cis
enyne-allene 7 followed by cycloaromatization to biradi-
cal 8 having a triarylmethyl radical center. While the
intrinsic rate of transformation from 7 to 8 was not
determined, the process was clearly facile at 25 °C due
mainly to the fixed s-cis structure in 7 and the stability
of the resulting triarylmethyl radical in 8.
† To whom correspondence concerning the X-ray structure should
be addressed.
X Abstract published in Advance ACS Abstracts, November 15, 1996.
(1) (a) Myers, A. G.; Kuo, E. Y.; Finney, N. S. J . Am. Chem. Soc.
1989, 111, 8057-8059. (b) Myers, A. G.; Dragovich, P. S. J . Am. Chem.
Soc. 1989, 111, 9130-9132. (c) Nagata, R.; Yamanaka, H.; Okazaki,
E.; Saito, I. Tetrahedron Lett. 1989, 30, 4995-4998. (d) Nagata, R.;
Yamanaka, H.; Murahashi, E.; Saito, I. Tetrahedron Lett. 1990, 31,
2907-2910. (e) Nicolaou, K. C.; Maligres, P.; Shin, J .; de Leon, E.;
Rideout, D. J . Am. Chem. Soc. 1990, 112, 7825-7926. For recent
reviews, see: (f) Wang, K. K. Chem. Rev. 1996, 96, 207-222. (g)
Grissom, J . W.; Gunawardena, G. U.; Klingberg, D.; Huang. D.
Tetrahedron 1996, 52, 6453-6518.
As a part of our continuing efforts in using the Myers
cyclization reaction to produce R,3-didehydrotoluene bi-
radicals having a persistent or stable benzylic radical
(2) Griller, D.; Ingold, K. U. Acc. Chem. Res. 1976, 9, 13-19.
(3) Wang, K. K.; Wang, Z.; Sattsangi, P. D. J . Org. Chem. 1996, 61,
1516-1518.
(4) Schreiner, K.; Berndt, A. Angew. Chem., Int. Ed. Engl. 1974,
13, 144-145.
(5) Naoe, Y.; Kikuishi, J .; Ishigaki, K.; Iitsuka, H.; Nemoto, H.;
Shibuya, M. Tetrahedron Lett. 1995, 36, 9165-9168.
S0022-3263(96)01073-0 CCC: $12.00 © 1996 American Chemical Society

8504 J . Org. Chem., Vol. 61, No. 24, 1996
Liu et al.
Sch em e 3
Sch em e 5
presence of cuprous bromide produced 18,9 which was
converted to 10 with iodine.10
Sch em e 4
While it was reported that treatment of benzaldehyde
with 18 led to the formation of triphenylallene in 85%
yield,9a attempts to transform 12a to 14a and 12b to 14b
with 18 gave very low yields (<4%). This difficulty was
circumvented by converting 18 to the iodide 10 followed
by treatment of 10 with n-butyllithium to produce the
corresponding alkenyllithium 11 for the subsequent
condensation with 12. It is worth noting that the iodide
10 is stable and can be prepared in large quantity for
subsequent use.
Enyne-allene 14a is thermally stable due to the
presence of a sterically demanding trimethylsilyl group
at the acetylenic terminus. However, when 14a in 1,4-
CHD was desilylated with tetrabutylammonium fluoride
(TBAF) to form the corresponding enyne-allene having
a hydrogen atom at the acetylenic terminus (R ) H),
cycloaromatization occurred at 37 °C in 4 h to furnish
20a (R ) H) in 41% yield (Scheme 5). Presumably, the
reaction proceeded through biradical 19a (R ) H) having
a triarylmethyl radical center followed by H-atom ab-
stractions from 1,4-CHD. Similarly, enyne-allenes 14b-e
cyclized at 65-80 °C in 1,4-CHD to afford 20b-e (Table
1). As in the case of 14a , the presence of a sterically
demanding tert-butyl group in 14f prevented cycloaro-
matization to 20f from occurring at 75 °C even after
prolonged heating.
center, we developed a new synthetic route to enyne-
allenes substituted with two phenyl groups at the ter-
minus of the allenic end. Cycloaromatization of these
enyne-allenes to form biradicals containing a stabilized
triarylmethyl radical center was also investigated.
Resu lts a n d Discu ssion
Our strategy for the synthesis of enyne-allenes 14
involved using the readily available enynyl aldehydes 126
for the Horner reaction7 with phosphinoxy carbanion 11
(Scheme 3). Carbanion 11 was prepared by treatment
of diphenyl(2,2-diphenyl-1-iodoethenyl)phosphine oxide
(10) with n-butyllithium at -78 °C. The condensation
reactions between 11 and 12 to form 13 appeared to be
very facile at -78 °C. When enynyl aldehydes 12 were
introduced, the dark red color of 11 disappeared almost
instantaneously. Elimination of lithium diphenylphos-
phinate from 13 also occurred spontaneously when the
reaction mixture was allowed to warm to rt, producing
enyne-allenes 14 in excellent isolated yields (Table 1).
The presence of the appropriately positioned benzylic
methyl group in 14e provides a route for intramolecular
H-atom abstraction to compete with intermolecular H-
atom transfer from 1,4-CHD leading to 20e. Indeed,
when enyne-allene 14e was heated under reflux in
benzene at 80 °C in the absence of 1,4-CHD for 96 h, 22
was produced in 40% isolated yield (Scheme 6). The
structure of 22 was unequivocally established by an X-ray
structure determination.11 Apparently, 19e leads to the
more stable biradical 21, which then undergoes an
intramolecular radical-radical combination to furnish
22. The fact that 22 was produced from 14e lends
support to the formation of R,3-didehydrotoluene biradi-
cals 19 as the transient reaction intermediates from
enyne-allenes 14. A cascade sequence similar to that
outlined in Scheme 6 to demonstrate the involvement of
10 was synthesized via the sequence outlined in
Scheme 4. Treatment of phenylacetylene (15) with
n-butyllithium followed by chlorodiphenylphosphine af-
forded 16.8 Subsequent oxidation of 16 with 30% H2O2
furnished diphenyl(phenylethynyl)phosphine oxide (17).8
Treatment of 17 with phenylmagnesium bromide in the
(6) (a) Saito, I.; Yamaguchi, K.; Nagata, R.; Murahashi, E. Tetra-
hedron Lett. 1990, 31, 7469-7472. (b) Wang, K. K.; Liu, B.; Lu, Y.-d.
Tetrahedron Lett. 1995, 36, 3785-3788. (c) Wang, K. K.; Liu, B.;
Petersen, J . L. J . Am. Chem. Soc. 1996, 118, 6860-6867.
(7) J ohnson, A. W.; Kaska, W. C.; Starzewski, K. A. O.; Dixon, D.
A. Ylides and Imines of Phosphorus; Wiley-Interscience: New York,
1993; p 314.
(9) (a) Marszak, M. B.; Simalty, M.; Seuleiman, A. Tetrahedron Lett.
1974, 1905-1908. (b) Aguiar, A. M.; Irelan, J . R. S. J . Org. Chem. 1969,
34, 4030-4031.
(10) Alexakis, A.; Cahiez, G.; Normant, J . F. Org. Synth. 1984, 62,
1-8.
(8) Charrier, C.; Simonnin, M.-P.; Chodkiewicz, W.; Cadiot, P.
Compt. Rend. 1964, 258, 1537-1540.

(4Z)-1,1-Diphenyl-1,2,4-heptatrien-6-ynes
J . Org. Chem., Vol. 61, No. 24, 1996 8505
yellow liquid: IR (neat) 2160, 1586, 1488, 1434, 1096, 1026,
Sch em e 6
839, 739, 690 cm-1 1H NMR (CDCl3) δ 7.85-7.78 (4 H, m),
;
7.67-7.63 (2 H, m), 7.49-7.40 (9 H, m); 13C NMR (CDCl3) δ
136.19 (d, J ) 6.7 Hz), 132.48 (d, J ) 20.9 Hz), 131.71, 128.95,
128.82, 128.55 (d, J ) 7.6 Hz), 128.26, 122.64, 107.71 (d, J )
3.8 Hz), 85.83 (d, J ) 6.7 Hz).
Dip h en yl(p h en yleth yn yl)p h osp h in e Oxid e (17).8 To a
solution of 16 (2.86 g, 10.0 mmol) in 30 mL of THF was added
2.5 mL of 30% H2O2 at 0 °C, and the mixture was stirred at 0
°C for 30 min. After an additional 2 h at rt, the mixture was
poured into a separatory funnel containing 50 mL of CH2Cl2
and 20 mL of water. The organic layer was separated, dried
over MgSO4, and concentrated to afford 2.57 g (85%) of 17 as
a yellow solid: IR (neat) 2173, 1589, 1486, 1438, 1200, 1115,
1
920, 847, 697, 644 cm-1; H NMR (CDCl3) δ 7.91-7.83 (4 H,
m), 7.56-7.29 (11 H, m); 13C NMR (CDCl3) δ 132.96 (d, J )
122.0 Hz), 132.47 (d, J ) 1.4 Hz), 132.20 (d, J ) 2.9 Hz), 130.91
(d, J ) 11.4 Hz), 130.67, 128.71, 128.52, 119.86 (d, J ) 3.8
Hz), 105.38 (d, J ) 30.0 Hz), 82.79 (d, J ) 169.7 Hz).
biradical species was previously employed in the Moore
Dip h en yl(2,2-d ip h en yl-1-iod oeth en yl)p h osp h in e Ox-
id e (10). To a solution containing 0.906 g (3.0 mmol) of 17
and 0.50 g (3.5 mmol) of CuBr was added 3.0 mL (3.0 mmol)
of a 1.0 M solution of phenylmagnesium chloride in THF, and
the resulting mixture was stirred at 50 °C for 6 h.9a Then 1.0
g (3.3 mmol) of iodine in 10 mL of THF was added at rt. After
3 h, the solution was poured into an aqueous solution of
Na2S2O3. The precipitate that formed was filtered, washed
with water (3 × 50 mL), and dried under vacuum to afford
1.4 g (92%) of 10 as a yellow solid: IR (KBr) 3052, 1529, 1488,
1438, 1181, 1113, 830, 750, 690 cm-1; 1H NMR (CDCl3) δ 7.75-
7.68 (4 H, m), 7.40-7.19 (11 H, m), 7.10-7.05 (2 H, m), 6.99-
6.88 (3 H, m); 13C NMR (CDCl3) δ 167.18 (d, J ) 6.7 Hz), 147.81
(d, J ) 12.4 Hz), 139.72 (d, J ) 5.2 Hz), 133.53 (d, J ) 109.2
Hz), 131.69 (d, J ) 9.5 Hz), 131.30, 129.58, 128.57, 128.40,
128.19, 128.02, 127.66, 97.72 (d, J ) 85.8 Hz); MS (m/ e) 506
(M+), 429, 379, 201.
cyclization of enyne-ketenes.12
Con clu sion s
We have developed a new synthetic pathway to enyne-
allenes having two phenyl substituents at the allenic
terminus. Thermolysis of these enyne-allenes produced
R,3-didehydrotoluene biradicals containing a reactive aryl
radical center and a stabilized triarylmethyl radical
center. The feasibility of converting the aryl radical
center in 19e to a more stable benzylic radical via an
intramolecular 1,5-hydrogen shift was also demonstrated.
The mildness of the thermal conditions makes cycloaro-
matization of enyne-allenes an especially attractive
process for designing entirely different strategies for the
synthesis of organic compounds containing multiple
stable radical centers, an area of intense current inter-
est.13
1,1-Dip h en yl-3-[[2-(tr im eth ylsilyl)eth yn yl]-1-cyclop en -
ten yl]-1,2-p r op a d ien e (14a ). The following procedure for the
preparation of 14a is representative. To a solution of 10 (0.253
g, 0.50 mmol) in 20 mL of THF was added 0.20 mL (0.50 mmol)
of a 2.5 M solution of n-BuLi in hexanes at -78 °C, and the
color of the solution changed to dark red immediately. After
30 min at -78 °C, 0.096 g (0.50 mmol) of the enynyl aldehyde
12a in 5 mL of THF was added. The color of the solution
changed to light yellow immediately. After 3 h, the mixture
was gradually warmed to rt, and a solid precipitate appeared
when the temperature reached 5 °C. After an additional 1 h
at rt, 100 mL of diethyl ether and 40 mL of water were added.
The organic layer was separated, washed with water (2 × 20
mL), dried over MgSO4, and concentrated. The residue was
purified by column chromatography (Florisil/hexanes) to afford
0.131 g (74%) of 14a as a yellow liquid: IR (neat) 2128, 1490,
1440, 1247, 842, 758, 694 cm-1; 1H NMR (CDCl3) δ 7.37-7.24
(10 H, m), 6.90 (1 H, s), 2.59 (2 H, t, J ) 7.5 Hz), 2.54 (2 H, t,
Exp er im en ta l Section
All reactions were conducted in oven-dried (120 °C) glass-
ware under a nitrogen atmosphere. Tetrahydrofuran (THF)
was distilled from benzophenone ketyl prior to use. n-
Butyllithium (2.5 M) in hexanes, chlorodiphenylphosphine, and
phenylacetylene were purchased from Aldrich Chemical Co.,
Inc. and were used as received. Silica gel (70-230 mesh) and
Florisil (100-200 mesh) for column chromatography were
purchased from Aldrich and Fisher, respectively. 1,4-Cyclo-
hexadiene was purchased from Wiley Organic, Inc. and was
used as received. Diphenyl(phenylethynyl)phosphine (16),8
diphenyl(phenylethynyl)phosphine oxide (17),8 and enynyl
aldehydes 126 were prepared according to the reported pro-
cedures. 1H (270 MHz) and 13C (67.9 MHz) NMR spectra were
recorded in CDCl3 using CHCl3 (1H δ 7.26) and CDCl3 (13C δ
77.02) as internal standard.
J ) 7.5 Hz), 1.89 (2 H, quintet, J ) 7.5 Hz), 0.22 (9 H, s); 13
C
NMR (CDCl3) δ 210.55, 145.07, 136.30, 128.55, 128.51, 127.47,
121.47, 112.01, 101.47, 93.71, 37.14, 33.69, 22.46, 0.22; MS
(m/ e) 354 (M+), 277, 261, 207, 175, 159, 135, 105.
Dip h en yl(p h en yleth yn yl)p h osp h in e (16).8 To a solution
of 2.50 g (25 mmol) of phenylacetylene in 20 mL of THF at
-20 °C was added 10 mL (25 mmol) of n-BuLi (2.5 M in
hexanes), and the mixture was stirred for 30 min. Then 5.1 g
(4.1 mL, 23 mmol) of chlorodiphenylphosphine was added at
-20 °C, and the reaction mixture was allowed to warm to rt.
After 2 h, the mixture was poured into 40 mL of water and
was extracted with methylene chloride (3 × 30 mL), dried over
MgSO4, and concentrated to furnish 6.29 g (92%) of 16 as a
1,1-Dip h en yl-3-[2-(1-h exyn yl)-1-cyclop en ten yl]-1,2-p r o-
p a d ien e (14b): isolated in 71% yield as a yellow liquid; 1H
NMR (CDCl3) δ 7.40-7.25 (10 H, m), 6.89 (1 H, s), 2.58-2.51
(4 H, m), 2.42 (2 H, t, J ) 6.9 Hz), 1.90 (2 H, quintet, J ) 7.5
Hz), 1.62-1.39 (4 H, m), 0.94 (3 H, t, J ) 7.3 Hz); 13C NMR
(CDCl3) δ 210.28, 141.46, 136.56, 128.56, 128.48, 127.37,
122.37, 111.80, 97.65, 93.70, 76.86, 37.54, 33.52, 31.13, 22.35,
22.11, 19.59, 13.75.
1,1-Dip h en yl-3-[2-(3-m et h yl-3-b u t en -1-yn yl)-1-cyclo-
p en ten yl]-1,2-p r op a d ien e (14c): isolated in 80% yield as a
yellow liquid; IR (neat) 2187, 1921, 1613, 1597, 1491, 1450,
(11) The authors have deposited atomic coordinates for this struc-
ture with the Cambridge Crystallographic Data Centre. The coordi-
nates can be obtained, on request, from the Director, Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge, CB2 1EZ,
UK.
(12) Chow, K.; Nguyen, N. V.; Moore, H. W. J . Org. Chem. 1990,
55, 3876-3880.
(13) Rajca, A. Chem. Rev. 1994, 94, 871-893.
1
1072, 1029, 897, 835, 768, 695, 633 cm-1; H NMR (CDCl3) δ
7.38-7.25 (10 H, m), 6.93 (1 H, s), 5.35 (1 H, br s), 5.26 (1 H,
br s), 2.62 (2 H, t, J ) 8.6 Hz), 2.59 (2 H, t, J ) 8.4 Hz), 1.98
(3 H, s), 1.94 (2 H, quintet, J ) 7.5 Hz); 13C NMR (CDCl3) δ
210.40, 143.34, 136.31, 128.48, 128.43, 127.37, 121.44, 111.92,
97.57, 93.64, 84.78, 77.23, 37.15, 33.67, 23.65, 22.38.

8506 J . Org. Chem., Vol. 61, No. 24, 1996
Ta ble 1. Syn th esis of En yn e-Allen es 14 a n d th e Cycloa r om a tized Ad d u cts 20
Liu et al.
R
14
isolated yield, %
20
isolated yield, %
reaction temp, °C
reaction time, h
Me3Si
Bu
isopropenyl
Ph
2-methylphenyl
tert-Bu
14a
14b
14c
14d
14e
14f
74
71
80
87
84
82
20a (R ) H)
41
57
44
52
61
37a
65
75
75
80
4
6
17
32
72
20b
20c
20d
20e
a
Enyne-allene 14a was first treated with TBAF followed by heating at 37 °C.
1,1-Dip h en yl-3-[2-(p h en ylet h yn yl)-1-cyclop en t en yl]-
MS (m/ e) 340 (M+), 283, 219, 205, 191, 165, 131, 115, 91;
HRMS calcd for C26H28 340.2191, found 340.2185.
1,2-p r op a d ien e (14d ): isolated in 87% yield as a yellow solid;
IR (neat) 2194, 1921, 1597, 1489, 1442, 1070, 1028, 910 cm-1
;
5-(Dip h en ylm et h yl)-6-(1-m et h ylet h en yl)in d a n (20c):
isolated by column chromatography (silica gel/2% diethyl ether
in hexanes) and HPLC (silica/1% diethyl ether in hexanes) in
44% yield as a white solid; IR (KBr) 1637, 1598, 1487, 1444,
1H NMR (CDCl3) δ 7.53-7.47 (2 H, m), 7.44-7.28 (13 H, m),
7.05 (1 H, s), 2.73 (2 H, t, J ) 7.4 Hz), 2.64 (2 H, t, J ) 7.4
Hz), 1.99 (2 H, t, J ) 7.5 Hz); 13C NMR (CDCl3) δ 210.45,
143.57, 136.28, 131.41, 128.48, 128.43, 128.29, 128.03, 127.38,
123.53, 121.44, 111.96, 96.33, 93.70, 85.84, 37.20, 33.75, 22.41.
1,1-Dip h en yl-3-[[2-(2-m et h ylp h en yl)et h yn yl]-1-cyclo-
p en ten yl]-1,2-p r op a d ien e (14e): isolated in 84% yield as a
yellow oil; IR (neat) 2191, 1920, 1597, 1490, 1451, 1030, 908,
834, 756, 694, 633 cm-1; 1H NMR (CDCl3) δ 7.48-7.13 (14 H,
m), 7.04 (1 H, s), 2.73 (2 H, t, J ) 7.4 Hz), 2.64 (2 H, t, J ) 7.5
Hz), 2.51 (3 H, s), 1.99 (2 H, quintet, J ) 7.5 Hz); 13C NMR
(CDCl3) δ 210.52, 143.04, 139.73, 136.30, 131.72, 129.40,
128.49, 128.44, 128.09, 127.40, 125.56, 123.33, 121.75, 111.95,
95.28, 93.73, 89.75, 37.34, 33.75, 22.42, 20.97.
1
893, 747, 728, 694 cm-1; H NMR (CDCl3) δ 7.27-7.13 (6 H,
m), 7.06 (4 H, d, J ) 6.9 Hz), 6.98 (1 H, s), 6.85 (1 H, s), 5.82
(1 H, s), 5.12 (1 H, m, J ) 1.8 Hz), 4.66 (1 H, m, J ) 1 Hz),
2.85 (2 H, t, J ) 7.4 Hz), 2.78 (2 H, t, J ) 7.5 Hz), 2.02 (2 H,
quintet, J ) 7.4 Hz), 1.84 (3 H, s); 13C NMR (CDCl3) δ 145.90,
144.88, 142.81, 142.15, 141.99, 138.05, 129.50, 128.12, 125.89,
123.88, 115.09, 52.53, 32.77, 32.54, 25.62, 25.43; MS (m/ e) 324
(M+) 309, 294, 265, 233, 218, 202, 165, 133, 115; HRMS calcd
for C25H24 324.1878, found 324.1861.
5-(Dip h en ylm et h yl)-6-p h en ylin d a n (20d ): isolated by
column chromatography (silica gel/2% diethyl ether in hex-
anes) and HPLC (silica/4% diethyl ether in hexanes) in 52%
yield as a light yellow oil; IR (neat) 1598, 1493, 1445, 1075,
3-[2-(3,3-Dim e t h yl-1-b u t yn yl)-1-cyclop e n t e n yl]-1,1-
d ip h en yl-1,2-p r op a d ien e (14f): isolated in 82% yield as a
yellow solid; IR (neat) 2209, 1921, 1670, 1597, 1490, 1447,
1
1030, 890, 749, 728, 689 cm-1; H NMR (CDCl3) δ 7.36-7.18
1
1360, 1272, 1202, 1176, 1119, 1072, 1029, 918, 900 cm-1; H
(10 H, m), 7.13-7.09 (3 H, m), 7.03-6.97 (4 H, m), 5.57 (1 H,
s), 2.93 (2 H, t, J ) 7.3 Hz), 2.89 (2 H, t, J ) 7.2 Hz), 2.10 (2
H, quintet, J ) 7.5 Hz); 13C NMR (CDCl3) δ 144.62, 143.39,
142.23, 142.04, 140.54, 139.24, 129.49, 129.43, 128.09, 127.79,
126.65, 125.91, 125.85, 52.94, 32.84, 32.55, 25.47; MS (m/ e)
360 (M+), 331, 309, 299, 265, 254, 205, 166, 152, 138, 127, 115;
HRMS calcd for C28H24 360.1878, found 360.1854.
NMR (CDCl3) δ 7.42-7.24 (10 H, m), 6.90 (1 H, s), 2.56 (2 H,
t, J ) 7.7 Hz), 2.54 (2 H, t, J ) 7.1 Hz), 1.90 (2 H, quintet, J
) 7.5 Hz), 1.31 (9 H, s); 13C NMR (CDCl3) δ 210.18, 141.32,
136.46, 128.47, 128.39, 127.28, 122.28, 111.72, 105.84, 93.63,
75.13, 37.45, 33.40, 31.23, 28.32, 22.28; MS (m/ e) 338 (M+),
323, 261, 245, 205, 183, 143, 115, 91; HRMS calcd for C26H26
338.2035, found 338.2043.
5-(Dip h en ylm et h yl)-6-(2-m et h ylp h en yl)in d a n (20e):
isolated by column chromatography and HPLC in 61% yield
as a light yellow oil; IR (neat) 1599, 1494, 1446, 1077, 1032,
5-(Dip h en ylm eth yl)in d a n (20a ). To a solution of enyne-
allene 14a (48.0 mg, 0.136 mmol) in 2.5 mL of 1,4-CHD was
added 0.3 mL of a 1.0 M solution of TBAF (0.3 mmol) in THF
at 0 °C. The mixture was then heated to 37 °C, and the
progress of the reaction was followed by TLC. After 4 h, the
starting material (the desilylated product of 14a ) disappeared
completely. The reaction mixture was concentrated, and the
residue was extracted with hexanes (2 × 20 mL), washed with
water (2 × 20 mL), dried over MgSO4, and concentrated. The
residue was purified by column chromatography (silica gel/
2% diethyl ether in hexanes) and then by HPLC (silica/2%
diethyl ether in hexanes) to afford 16 mg (41%) of 20a as a
colorless liquid: IR (neat) 1599, 1493, 1448, 1077, 1031, 909,
819, 732, 699, 612 cm-1; 1H NMR (CDCl3) δ 7.38-7.08 (11 H,
m), 6.99 (1 H, s), 6.89 (1 H, d, J ) 7.7 Hz), 5.53 (1 H, s), 2.88
(2 H, t, J ) 7.7 Hz), 2.84 (2 H, t, J ) 7.7 Hz), 2.05 (2 H, quintet,
J ) 7.4 Hz); 13C NMR (CDCl3) δ 144.38, 144.30, 142.20, 141.80,
129.44, 128.24, 127.36, 126.15, 125.39, 124.07, 56.75, 32.84,
32.47, 25.47; MS (m/ e) 284 (M+), 256, 241, 207, 178, 165, 128,
115, 91; HRMS calcd for C22H20 284.1565, found 284.1559.
5-Bu tyl-6-(d ip h en ylm eth yl)in d a n (20b). The following
908, 754, 729, 699, 650 cm-1 1H NMR (CDCl3) δ 7.35-7.02
;
(10 H, m), 6.98-6.90 (5 H, m), 6.85 (1 H, d, J ) 7.3 Hz), 5.28
(1 H, s), 2.90 (2 H, t, J ) 7.1 Hz), 2.88 (2 H, t, J ) 7.3 Hz),
2.09 (2 H, quintet, J ) 7.4 Hz), 1.85 (3 H, s); 13C (CDCl3) δ
144.25, 143.71, 143.15, 141.97, 141.33, 139.87, 139.76, 136.35,
130.06, 129.72, 129.55, 129.43, 128.01, 127.99, 127.03, 125.90,
125.85, 125.47, 125.06, 53.22, 32.86, 32.54, 25.40, 20.03; MS
(m/ e) 374 (M+), 359, 331, 295, 281, 252, 219, 203, 165, 134,
91, 77. Because of steric interactions, there is a high energy
barrier for the the rotation about the carbon-carbon single
bonds attaching the diphenylmethyl group and the methylphe-
nyl group to the benzene ring of indan. Consequently, ad-
ditional 13C NMR signals due to the two nonequivalent phenyls
of the diphenylmethyl group were observed.
7,7-Dip h en yl-6,7,16,17-tetr a h yd r o-15H-cyclop en ta [b]-
p h en a n th r en e (22). To a flask attached with a reflux
condenser containing 102 mg (0.274 mmol) of 14e was added
220 mL of distilled benzene. The mixture was degassed by
bubbling nitrogen through it for 5 min and then was heated
to reflux. The progress of the reaction was followed by TLC,
and the starting enyne-allene 14e disappeared after 4 days.
Benzene was removed by distillation, and the residue was
filtered through a short silica gel column using 2% diethyl
ether in hexanes as the eluting solvent to furnish a yellow oil
in 56% yield. In addition, a brown mixture which was
insoluble in hexanes was also obtained in 26% yield by weight.
The yellow oil was further purified by column chromatography
(silica gel/2% diethyl ether in hexanes) and HPLC (silica/1%
diethyl ether in hexanes) to afford 41 mg (40%) of 22 as a light
yellow oil along with an unidentified yellow oil in 11% yield
by weight. When 22 was redissolved in diethyl ether and the
solvent was then evaporated in vacuo, a colorless crystal was
formed. 22: IR (neat) 1597, 1487, 1445, 1117, 1035, 994, 882,
procedure for the preparation of 20b is representative.
A
solution of enyne-allene 14b (61 mg, 0.18 mmol) in 2.5 mL of
1,4-CHD was heated at 65 °C, and the progress of the reaction
was followed by TLC. After 6 h at 65 °C, the starting enyne-
allene 14b disappeared completely. The reaction mixture was
concentrated, and the residue was purified by column chro-
matography (silica gel/hexanes) to afford 35 mg (57%) of 20b
as a colorless liquid and 14 mg (22%) of an unidentified yellow
liquid. 20b: IR (neat) 1599, 1492, 1447, 1076, 1030, 749, 699,
624 cm-1; 1H NMR (CDCl3) δ 7.34-7.15 (6 H, m), 7.1-7.03 (5
H, m), 6.69 (1 H, s), 5.74 (1 H, s), 2.86 (2 H, t, J ) 7.4 Hz),
2.76 (2 H, t, J ) 7.4 Hz), 2.52 (2 H, t, J ) 8.0 Hz), 2.01 (2 H,
quintet, J ) 7.4 Hz), 1.52-1.40 (2 H, m), 1.32 (2 H, sextet, J
) 7.3 Hz), 0.86 (3 H, t, J ) 7.2 Hz); 13C NMR (CDCl3) δ 144.25,
142.25, 141.47, 139.39, 138.95, 129.60, 128.20, 126.05, 125.74,
125.39, 52.64, 33.82, 32.70, 32.64, 32.58, 25.41, 22.90, 13.99;
1
754, 732, 695 cm-1; H NMR (CDCl3) δ 7.69 (1 H, s), 7.60 (1
H, d, J ) 7.5 Hz), 7.22-7.05 (13 H, m), 6.99 (1 H, s), 3.74 (2

(4Z)-1,1-Diphenyl-1,2,4-heptatrien-6-ynes
J . Org. Chem., Vol. 61, No. 24, 1996 8507
H, s), 2.98 (2 H, t, J ) 7.4 Hz), 2.83 (2 H, t, J ) 7.4 Hz), 2.09
(2 H, quintet, J ) 7.5 Hz); 13C NMR (CDCl3) δ 146.13, 143.48,
143.20, 141.58, 135.43, 134.84, 132.98, 129.22, 128.08, 127.65,
126.97, 126.73, 126.07, 125.60, 123.18, 120.24, 53.16, 43.26,
32.94, 32.73, 25.44; MS (m/ e) 372 (M+), 295, 267, 252, 165,
126, 77; HRMS calcd for C29H24 372.1878, found 372.1871. 22
was recrystallized from a mixture of diethyl ether and hexanes
(7:3) for the X-ray structure determination.11
tion Program of the National Science Foundation (Grant
CHE-9120098) for the acquisition of a Siemens P4 X-ray
diffractometer by the Department of Chemistry at West
Virginia University.
Su p p or t in g In for m a t ion Ava ila b le: 1H and 13C NMR
spectra of 10, 14a -f, 20a -e, and 22 (27 pages). This material
is contained in libraries on microfiche, immediately follows this
article in the microfilm version of the journal, and can be
ordered from the ACS; see any current masthead page for
ordering information.
Ack n ow led gm en t. The financial support of the
National Science Foundation (Grant CHE-9307994) to
K.K.W. is gratefully acknowledged. J .L.P. acknowl-
edges financial support by the Chemical Instrumenta-
J O961073X