The BF3*Et2O-Catalyzed Reaction of 1,2-Biscyclobutene and Analogues with Aromatic Ketones

Full text of DOI:10.1021/jo971867r

1352
J . Org. Chem. 1998, 63, 1352-1355
Sch em e 1
Th e BF 3‚Et2O-Ca ta lyzed Rea ction of
1,2-Bis[(tr im eth ylsilyl)oxy]cyclobu ten e a n d
An a logu es w ith Ar om a tic Keton es
Sheldon N. Crane and D. J ean Burnell*
Department of Chemistry, Memorial University of
Newfoundland, St. J ohn’s, Newfoundland A1B 3X7, Canada
Received October 9, 1997
Ketones1 and their acetals2-5 in the presence of a Lewis
acid, usually BF3‚Et2O, were shown to react with 1,2-
bis((trimethylsilyl)oxy)cyclobutene (1) and its methylated
analogues 2 and 36 to give cyclobutanone derivatives 4a -
c, and these could be rearranged to give geminally
acylated compounds 5a -c (Scheme 1). Geminal acyla-
tions with 1 have been employed in a number of synthetic
endeavors.3,7,8 In the particular case of the reactions with
ketones, cyclobutanone intermediates 4a -c were rear-
ranged in the same pot to give 5a -c by addition of water
and excess BF3‚Et2O. The one-pot procedure with 1 and
2 provided good to excellent yields of 5a and 5b when
the substrates were unhindered,1,3-6 whereas yields of
5c using 3 were usually modest, even with unhindered
ketones.6 Reactions of some R,â-unsaturated ketones
with 3 provided 5c with yields around 80%, but, unlike
the reactions of their saturated counterparts, enone
substrates afforded 5c directly, without the addition of
water and excess BF3‚Et2O. This might be attributed to
allylic stabilization of a positive charge in the transition
state of the rearrangement. We reasoned that a similar
benzylic stabilization could arise with aromatic ketones,
which might lead to an improvement in the procedure
for the reaction of these substrates with 1 and an
opportunity to carry out geminal acylation of aromatic
ketones with both 2 and 3.
equiv of BF3‚Et2O were employed. The reaction mixture
was stirred at room temperature for approximately 24
h. Straightforward aqueous workup followed by flash
chromatography provided the geminally acylated product,
a 1,3-diketone. The results are summarized in Table 1.
The yields of 6, 7, 8, and 10 (from 1 with acetophenone,
1-indanone, 1-tetralone, and 4-chromanone) were similar
to the yields by the earlier procedure that involved adding
H2O to the reaction mixture,1 which in turn were gener-
ally better than the reactions with acetals derived from
aromatic ketones.4,5 The acetal of benzophenone was
reported by Ayyangar5 to react with 1 to give only a trace
of 12, whereas the conversion of benzophenone to 12 was
75% under these anhydrous conditions. The reactions
with 1-tetralone, 4-chromanone, and benzophenone also
gave minor amounts of lactones 9, 11a ,b, and 13,
respectively. Similar lactones had been observed in the
reactions of enones with 3,6 and Pandey reported the
photochemical conversion of 7 and 8 to the corresponding
lactones.8 In our case, we postulate the formation of
these lactones by the process shown in Scheme 2. Acid-
promoted elimination of the benzylic oxygen function in
4a could lead not only to 1,2-acyl shift (and thence to 5a )
but also to rupture of the four-membered ring to produce
the acylium ion in 27. Attack of the conjugated enol
moiety onto the acylium ion would give the lactone.
Five aromatic substrates were subjected to very similar
reaction conditions. For 1 and 2, the ketone and 1.5
equiv of freshly distilled BF3‚Et2O were dissolved in dry
CH2Cl2, and 2-3 equiv of the bis((trimethylsilyl)oxy)-
cyclobutene were added while maintaining anhydrous
conditions. For 3, the only difference was that up to 3
(1) J enkins, T. J .; Burnell, D. J . J . Org. Chem. 1994, 59, 1485-
1491.
Yields in the reactions of (racemic) 2 with the five
substrates mirrored those with 1: 1-tetralone and 4-chro-
manone gave lower yields, near 50%. Unlike the prod-
ucts derived from 1 and 3, those from 2 were complicated
by diastereoisomerism, except in the case of 18. Very
modest stereochemical preferences were noted, with
acetophenone showing the largest stereoselectivity, albeit
only 2.6:1. When acetals were prepared from acetophe-
none, 1-indanone, and 1-tetralone, and these were re-
acted with 2, geminal acylation products were obtained
in slightly lower yields and again with modest diaste-
reoselectivities. Production of the isomer that had been
more abundant from the ketone reactions was reduced
in the reactions with acetals. In the cases of 1-indanone
and 1-tetralone, the diastereoselectivities were opposite
to the reactions of their corresponding acetals. AM1
calculations9 gave no difference in the energies of 14a
and 14b, so any stereoselectivity was likely to be the
(2) Shimada, J .; Hashimoto, K.; Kim, B. H.; Nakamura, E.; Kuwa-
jima, I. J . Am. Chem. Soc. 1984, 106, 1759-1773.
(3) Burnell, D. J .; Wu, Y.-J . Can. J . Chem. 1990, 68, 804-811.
(4) Wu, Y.-J .; Strickland, D. W.; J enkins, T. J .; Liu, P.-Y.; Burnell,
D. J . Can. J . Chem. 1993, 71, 1311-1318.
(5) Pandey, B.; Khire, U. R.; Ayyangar, N. R. Synth. Commun. 1989,
19, 2741-2747.
(6) Crane, S. N.; J enkins, T. J .; Burnell, D. J . J . Org. Chem. 1997,
62, 8722-8729.
(7) (a) Anderson, W. K.; Lee, G. E. J . Org. Chem. 1980, 45, 501-
506. (b) Oppolzer, W.; Wylie, R. D. Helv. Chim. Acta 1980, 63, 1198-
1203. (c) Parker, K. A.; Koziski, K. A.; Breault, G. Tetrahedron Lett.
1985, 26, 2181-2184. (d) Burnell, D. J .; Wu, Y.-J . Can. J . Chem. 1989,
67, 816-819. (e) Saint-J almes, L.; Lila, C.; Xu, J . Z.; Moreau, L.;
Pfeiffer, B.; Eck, G.; Pelsez, L.; Rolando, C.; J ulia, M. Bull. Soc. Chim.
Fr. 1993, 130, 447-449. (f) Wu, Y.-J .; Zhu, Y.-Y.; Burnell, D. J . J . Org.
Chem. 1994, 59, 104-110. (g) Wendt, J . A.; Gauvreau, P. J .; Bach, R.
D. J . Am. Chem. Soc. 1994, 116, 9921-9926. (h) Balog, A.; Curran, D.
P. J . Org. Chem. 1995, 60, 337-344. (i) Balog, A.; Geib, S. J .; Curran,
D. P. J . Org. Chem. 1995, 60, 345-352. (j) Zhu, Y.-Y., Burnell, D. J .
Tetrahedron: Asymmetry 1996, 7, 3295-3304. (k) Liu, P.-Y.; Wu, Y.-
J .; Burnell, D. J . Can. J . Chem. 1997, 75, 656-664.
(8) Pandey, B.; Reddy, R. S.; Kumar, P. J . Chem. Soc., Chem.
Commun. 1993, 870-871.
S0022-3263(97)01867-7 CCC: $15.00 © 1998 American Chemical Society
Published on Web 02/04/1998

Notes
J . Org. Chem., Vol. 63, No. 4, 1998 1353
Ta ble 1. P r od u cts a n d Yield s in th e Rea ction s of F ive Ar om a tic Keton es w ith Cyclobu ten es 1-3
Sch em e 2
was the dominant component of the product, which also
contained small amounts of isomeric compounds that
were inseparable by flash chromatography. The reac-
tions of 3 with 1-tetralone and 4-chromanone provided
minor, but significant, amounts of the lactone pairs 22a ,b
and 24a ,b (2.6:1 ratio in each case), and NOE measure-
ments indicated that the E-isomer was the more abun-
dant isomer.10 A lactone 26 was also a byproduct of the
reaction with benzophenone. Solutions of diketone 23
in CH2Cl2 were stirred for 24 h at room temperature with
4 equiv of BF3‚Et2O under anhydrous conditions, and
with 15 equiv of BF3‚Et2O and 6 equiv of water. In
neither case were lactones 24a ,b observed. Furthermore,
when the reaction of 3 with acetophenone was conducted
at -20 °C it was possible to intercept two diastereomeric
cyclobutanone intermediates 28 and 29, in a 5.7:1 ratio.11
consequence of a kinetically controlled process. We
suggest that the stereoselectivity was a result of facial
selectivity in the initial aldol process since a regiochemi-
cal preference in the initial aldol step (to produce 4b or
its positional isomer) would have no remaining manifes-
tation in a racemic product. It was curious that lactone
products were not isolated from the reactions with 2,
although small amounts of carbonyl-containing secondary
products were detected.
(The relative stereochemistry of the minor product was
determined by X-ray crystallography.12) Thus, the regi-
oselectivity of the initial aldol step was very high, and
facial selectivity was responsible for the production of 28
Geminal acylation using 3 with the five substrates gave
1,3-diketones in moderate yield. With acetophenone, 19
(10) The 1H NMR spectra of the (minor) Z-lactones 22b and 24b
showed one aromatic resonance just downfield of δ 8. This feature was
used to assign the Z-lactone structures to 9 and 11b.
(11) Similar attempts to obtain cyclobutanone intermediates from
1-indanone and 1-tetralone at -20 °C gave only the 1,3-diketone and
lactone products.
(9) Dewar, M. J . S.; Zoebisch, E. G.; Healy, E. F.; Stewart, J . J . P.
J . Am. Chem. Soc. 1985, 107, 3902-3909 using SPARTAN, Version
4.1 (Wavefunction, Inc., Irvine, CA).

1354 J . Org. Chem., Vol. 63, No. 4, 1998
Notes
7.19 (2H, m), 2.98 (1H, dd, J ) 9.6, 16.7 Hz), 2.86 (1H, m), 2.53
(1H, dd, J ) 8.6, 16.7 Hz), 1.47 (3H, s), 1.29 (3H, d, J ) 7.1 Hz);
NOE data 2.53 (2.98, 6%; 2.86, 4%), 1.43 (7.22, 8%; 2.86, 2%);
13C NMR δ 216.2 (0), 212.7 (0), 137.0 (0), 129.0 (2C, 1), 127.7
(1), 126.4 (2C, 1), 61.0 (0), 43.7 (2), 42.0 (1), 20.8 (3), 16.9 (3).
(2R*,4R*)-2′,3′-Dih yd r o-4-m eth ylsp ir o(cyclop en ta n e-2,1′-
over 29. The process shown in Scheme 2 would also
account for the formation 22a ,b, 24a ,b, and 26 from 4c.
In summary, geminal acylation of aromatic ketones
with 1 and its methylated analogues 2 and 3 can take
place in fair to good yield. In contrast with the process
for the geminal acylation of saturated ketones, both steps
in the geminal acylation of aromatic and R,â-unsaturated
ketones occur readily under anhydrous conditions.
1
[1H]in d en e)-1,3-d ion e (15a ). Viscous, yellow oil; H NMR δ
7.30 (1H, d, J ) 8.0 Hz), 7.23 (1H, apparent t, J ) 7.4 Hz), 7.15
(1H, apparent t, J ) 7.2 Hz), 6.93 (1H, d, J ) 7.7 Hz), 3.32 (1H,
m), 3.29-3.09 (3H, m), 2.59-2.32 (2H, m), 2.49 (1H, m), 1.37
(3H, d, J ) 7.3 Hz); 13C NMR δ 214.9 (0), 212.8 (0), 144.6 (0),
141.0 (0), 128.1 (1), 126.7 (1), 125.2 (1), 122.2 (1), 69.5 (0), 44.1
(2), 41.6 (1), 32.6 (2), 31.6 (2), 15.1 (3).
Exp er im en ta l Section
Gen er a l Section . Compounds 1-3 were obtained by using
the method for the preparation of 1 of Bloomfield and Nelke.13
1H NMR spectra were obtained at 300 MHz in CDCl3 unless
specified otherwise, and shifts are relative to internal TMS. NOE
measurements were made from difference spectra and are
reported as the saturated signal (observed signal, enhancement).
13C NMR spectra were recorded at 75 MHz. Chemical shifts
are relative to solvent, and each 13C chemical shift is followed
in parentheses by the number of attached protons as determined
by APT and heteronuclear correlation spectra.
Gen er a l P r oced u r e. 2-Meth yl-2-p h en ylcyclop en ta n e-
1,3-d ion e (6). A solution of acetophenone (241 mg, 2.01 mmol),
1 (0.73 g, 3.2 mmol), and freshly distilled BF3‚Et2O (0.30 mL,
2.4 mmol) in CH2Cl2 (10 mL, distilled from CaH2) was stirred
at rt under N2 for 25.5 h. Aqueous workup provided a viscous
tan-colored oil (406 mg). Flash chromatography (MeOH-CH2-
Cl2 1:200) afforded 6 as a very pale yellow oil (267 mg, 70%).
Spectra were the same as previously reported.4 Spectra for 7
and 8 also were reported in previous work.1
3,4-Dih yd r o-5-(1-n a p h th ylid en e)-2-fu r a n on e (9). Beige
solid; 1H NMR δ 8.04 (1H, d, J ) 7.7 Hz), 7.24-7.06 (3H, m),
3.01 (2H, apparent t, J ) 8.6 Hz), 2.85-2.66 (4H, m), 2.37 (2H,
apparent t, J ) 6.2 Hz), 1.86 (2H, apparent t, J ) 6.3 Hz).
1′,2′,3′,4′-Tetr ah ydr o-4′-oxaspir o[cyclopen tan e-1,1′-n aph -
th a len e]-2,5-d ion e (10). Pale yellow solid, mp 110-111.5 °C;
1H NMR δ 7.19 (1H, apparent dt, J ) 1.3, 7.7 Hz), 6.91 (1H, d,
J ) 7.3 Hz), 6.85 (1H, apparent t, J ) 7.5 Hz), 6.58 (1H, dd, J
) 1.6, 7.7 Hz), 4.33 (2H, apparent t, J ) 5.2 Hz), 3.02 (4H,
symmetric m), 2.08 (2H, apparent t, J ) 5.1 Hz); 13C NMR δ
213.6 (2C, 0), 155.2 (0), 129.2 (1), 128.0 (1), 120.9 (1), 117.7 (1),
117.6 (0), 60.7 (2), 60.0 (0), 35.2 (2C, 2), 28.9 (2).
3,4-Dih yd r o-5-(1-(1′,2′,3′,4′-t e t r a h yd r o-4-oxa n a p h t h -
ylid en e))-2-fu r a n on e (11a ,b). Gummy, yellow solid (1.5:1
mixture of geometric isomers). Major isomer: 1H NMR (discern-
ible signals) δ 7.19 (1H, br d, J ) 7.8 Hz), 2.53 (2H, br t). Minor
isomer: 1H NMR (discernible signals) δ 8.10 (1H, dd, J ) 1.6,
8.0 Hz), 3.25 (2H, br t). 13C NMR (signals for both isomers) δ
174.9/174.0 (0), 154.6/153.7 (0), 143.5/142.5 (0), 108.3/104.7 (0),
65.9/65.5 (2).
(2R*,4S*)-2′,3′-Dih yd r o-4-m eth ylsp ir o(cyclop en ta n e-2,1′-
[1H]in d en e)-1,3-d ion e (15b). Viscous, pale yellow oil; 1H NMR
δ 7.30 (1H, d, J ) 7.5 Hz), 7.24 (1H, apparent t, J ) 7.2 Hz),
7.16 (1H, apparent t, J ) 7.4 Hz), 6.83 (1H, d, J ) 7.1 Hz), 3.26-
3.09 (3H, m), 3.02 (1H, m), 2.62 (1H, dd, J ) 9.6, 18.0 Hz), 2.49-
2.26 (2H, m), 1.41 (3H, d, J ) 6.8 Hz); NOE data 6.83 (2.62,
1%), 2.62 (6.83, 2%; 3.19 dd, 6%; 3.02, 2%; 1.41, 1%), 1.41 (6.83,
2%; 3.02, 5%; 2.62, 4%); 13C NMR δ 216.3 (0), 212.7 (0), 145.3
(0), 140.8 (0), 128.1 (1), 126.8 (1), 124.9 (1), 123.2 (1), 69.1 (0),
44.5 (2), 41.9 (1), 35.6 (2), 31.5 (2), 15.1 (3).
(2R*,4R*)-1′,2′,3′,4′-Tetr a h yd r o-4-m eth ylsp ir o[cyclop en -
ta n e-2,1′-n a p h th a len e]-1,3-d ion e (16a ). Yellow resin; 1H
NMR δ 7.23-7.12 (2H, m), 7.08 (1H, m), 6.56 (1H, d, J ) 7.6
Hz), 3.11 (1H, m), 3.08-2.92 (2H, m), 2.85 (2H, m), 2.69 (1H, br
dd, J ) 8.5, 16.1 Hz), 2.14-1.79 (4H, m), 1.45 (3H, d, J ) 7.1
Hz); 13C NMR δ 217.0 (0), 214.8 (0), 138.4 (0), 132.2 (0), 129.9
(1), 127.9 (1), 127.5 (1), 126.3 (1), 61.5 (0), 43.7 (1), 43.2 (2), 31.5
(2), 28.7 (2), 18.0 (2), 16.5 (3).
(2R*,4S*)-1′,2′,3′,4′-Tetr a h yd r o-4-m eth ylsp ir o[cyclop en -
1
ta n e-2,1′-n a p h th a len e]-1,3-d ion e (16b). Colorless resin; H
NMR δ 7.22-7.12 (2H, m), 7.09 (1H, m), 6.48 (1H, d, J ) 7.8
Hz), 3.32 (1H, dd, J ) 10.4, 18.2 Hz), 3.20 (1H, m), 2.84 (2H,
m), 2.48 (1H, dd, J ) 8.6, 18.4 Hz), 2.11-1.81 (4H, m), 1.37 (3H,
d, J ) 6.6 Hz); NOE data 2.48 (6.48, 1%; 3.32, 5%; 3.20, 3%),
1.37 (6.48, 2%; 3.20, 6%; 2.48, 4%); 13C NMR δ 217.2 (0), 213.9
(0), 138.5 (0), 132.0 (0), 129.6 (1), 128.7 (1), 127.5 (1), 126.2 (1),
63.0 (0), 44.6 (2), 40.0 (1), 32.1 (2), 28.7 (2), 18.0 (2), 15.4 (3).
(2R*,4R*)-1′,2′,3′,4′-Tetr a h yd r o-4-m eth yl-4-oxa sp ir o[cy-
clop en ta n e-2,1′-n a p h th a len e]-1,3-d ion e (17a ). White resin;
1H NMR δ 7.17 (1H, ddd, J ) 1.5, 7.2, 8.4 Hz), 6.90 (1H, dd, J
) 0.9, 8.3 Hz), 6.83 (1H, ddd, J ) 1.3, 7.2, 7.8 Hz), 6.60 (1H, dd,
J ) 1.6, 7.8 Hz), 4.43 (1H, ddd, J ) 4.2, 6.8, 11.0 Hz), 4.32 (1H,
ddd, J ) 4.0, 7.0, 11.6 Hz), 3.25-3.05 (2H, m), 2.64 (1H, m),
2.06 (2H, m), 1.43 (3H, d, J ) 7.0 Hz); 13C NMR δ 215.6 (0),
213.5 (0), 155.1 (0), 129.2 (1), 127.6 (1), 120.9 (1), 118.0 (1), 117.9
(0), 61.1 (2), 56.2 (0), 43.4 (1), 43.3 (2), 28.9 (2), 16.0 (3).
(2R*,4S*)-1′,2′,3′,4′-Tetr a h yd r o-4-m eth yl-4-oxa sp ir o[cy-
clop en ta n e-2,1′-n a p h th a len e]-1,3-d ion e (17b). White resin;
1H NMR δ 7.19 (1H, m), 6.90 (1H, m), 6.85 (1H, m), 6.50 (1H,
dd, J ) 1.6, 7.8 Hz), 4.30 (2H, symmetric m), 3.31 (1H, dd, J )
10.5, 18.4 Hz), 3.16 (1H, m), 2.09 (2H, symmetric m), 2.56 (1H,
dd, J ) 9.1, 18.4 Hz), 1.41 (3H, d, J ) 7.1 Hz); NOE data 2.56
(6.50, 1%; 3.31, 7%, 3.16, 2%, 1.41, 1%), 1.37 (6.50, 2%; 3.16,
5%, 2.56, 3%); 13C NMR δ 216.3 (0), 212.7 (0), 155.5 (0), 129.3
(1), 128.6 (1), 121.0 (1), 118.0 (0), 117.7 (1), 60.8 (2), 57.8 (0),
44.7 (2), 40.4 (1), 29.9 (2), 15.3 (3).
2,2-Dip h en ylcyclop en ta n e-1,3-d ion e (12). Pale yellow
solid, mp 158-160 °C; 1H NMR δ 7.40-7.28 (6H, m), 7.12-7.04
(4H, m), 2.96 (4H, s); 13C NMR δ 211.3 (2C, 0), 136.5 (2C, 0),
128.9 (1), 128.1 (1), 72.2 (0), 36.0 (2C, 2).
3,4-Dih ydr o-5-(diph en ylm eth ylen e)-2-fu r an on e (13). Yel-
1
low solid, mp 103.5-106.5 °C; H NMR δ 7.44-7.16 (10H, m),
2.92 (2H, dd, J ) 9.1, 11.1 Hz), 2.70 (2H, dd, J ) 9.0, 10.9 Hz);
13C NMR δ 174.7 (0), 146.2 (0), 138.7 (0), 137.5 (0), 129.9 (2C,
1), 129.2 (2C, 1), 128.6 (2C, 1), 127.9 (2C, 1), 127.3 (1), 126.8 (1),
118.5 (0), 27.5 (2), 25.9 (2).
4-Meth yl-2,2-d ip h en ylcyclop en ta n e-1,3-d ion e (18). Yel-
low solid, mp 86.5-88.5 °C; 1H NMR δ 7.40-7.27 (6H, m), 7.20-
7.12 (2H, m), 7.30-6.95 (2H, m), 3.20 (1H, dd, J ) 10.6, 17.9
Hz), 3.07 (1H, m), 2.54 (1H, dd, J ) 8.7, 17.9 Hz), 1.35 (3H, d,
J ) 7.0 Hz); 13C NMR δ 213.6 (0), 210.7 (0), 137.3 (0), 136.4 (0),
129.8 (1), 128.9 (1), 128.5 (1), 128.4 (1), 128.0 (1), 127.9 (1), 127.6
(1), 44.3 (2), 41.8 (1), 15.6 (3).
(2R *,4R *)-2,4-Dim e t h yl-2-p h e n yl-1,3-cyclop e n t a n e d i-
1
on e (14a ). Colorless oil; H NMR δ 7.39-7.25 (3H, m), 7.25-
7.17 (2H, m), 3.13 (1H, dd, J ) 11.7, 18.2 Hz), 3.01 (1H, m),
2.34 (1H, dd, J ) 8.0, 18.2 Hz), 1.43 (3H, s), 1.28 (3H, d, J ) 6.9
Hz); 13C NMR δ 215.0 (0), 212.6 (0), 137.4 (0), 129.3 (2C, 1), 127.8
(1), 126.2 (2C, 1), 62.1 (0), 43.9 (2), 40.8 (1), 20.1 (3), 14.7 (3).
(2R *,4S *)-2,4-Dim e t h yl-2-p h e n yl-1,3-cyclop e n t a n e d i-
on e (14b). Pale yellow oil; 1H NMR δ 7.40-7.25 (3H, m), 7.25-
2,4,4-Tr im eth yl-2-ph en ylcyclopen tan e-1,3-dion e (19). Pale
1
yellow oil; H NMR δ 7.40-7.20 (5H, m), 2.77 (1H, d, J ) 17.4
Hz), 2.58 (1H, d, J ) 17.4 Hz), 1.47 (3H, s), 1.24 (3H, s), 1.23
(3H, s); 13C NMR δ 218.3 (0), 213.2 (0), 137.4 (0), 129.1 (2C, 1),
127.7 (1), 126.2 (2C, 1), 60.9 (0), 50.8 (2), 46.9 (0), 26.2 (3), 25.8
(3), 22.0 (3).
(12) Atomic coordinates for the X-ray structure of 29 have been
deposited with the Cambridge Crystallographic Data Centre. A request
for these coordinates should be addressed to the Director, Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CD2 1EZ,
UK.
(13) Bloomfield, J . J .; Nelke, J . M. Organic Syntheses; Wiley: New
York, 1988; Collect. Vol. VI, pp 167-172.
2′,3′-Dih yd r o-4,4-d im eth ylsp ir o[cyclop en ta n e-2,1′-[1H]-
in d en e]-1,3-d ion e (20). Yellow solid, mp 65-66.5 °C; 1H NMR
δ 7.28 (1H, apparent t, J ) 7.0 Hz), 7.23 (1H, apparent dt, J )
1.2, 7.4 Hz), 7.15 (1H, apparent t, J ) 7.1 Hz), 6.85 (1H, d, J )
7.5 Hz), 3.18 (2H, m), 2.87 (1H, d, J ) 17.7 Hz), 2.76 (1H, d, J

Notes
J . Org. Chem., Vol. 63, No. 4, 1998 1355
) 17.6 Hz), 2.50-2.30 (2H, m), 1.39 (3H, s), 1.30 (3H, s); 13C
NMR δ 218.9 (0), 213.0 (0), 145.3 (0), 141.2 (0), 128.2 (1), 126.9
(1), 125.1 (1), 123.0 (1), 68.4 (0), 51.5 (2), 46.9 (0), 36.2 (2), 31.8
(2), 25.8 (3), 24.0 (3).
1′,2′,3′,4′-Tet r a h yd r o-4,4-d im et h ylsp ir o[cyclop en t a n e-
2,1′-n a p h th a len e]-1,3-d ion e (21). Pale yellow solid, mp 97-
98.5 °C; 1H NMR δ 7.24-7.04 (3H, m), 6.55 (1H, d, J ) 7.8 Hz),
2.98 (1H, d, J ) 18.3 Hz), 2.85 (2H, apparent t, J ) 6.0 Hz),
2.70 (1H, d, J ) 18.3 Hz), 2.10-1.88 (4H, m), 1.44 (3H, s), 1.34
(3H, s); 13C NMR δ 219.7 (0), 214.6 (0), 138.5 (0), 132.0 (0), 129.8
(1), 128.5 (1), 127.6 (1), 126.3 (1), 62.7 (0), 50.7 (2), 46.5 (0), 32.7
(2), 28.7 (2), 26.6 (3), 26.0 (3), 18.0 (2).
3,4-Dih yd r o-3,3-d im et h yl-5-(1-(1,2,3,4-t et r a h yd r on a p h -
th ylid en e))-2-fu r a n on e (22a ,b). Major isomer 22a : beige
solid, mp 69-71.5 °C; 1H NMR δ 7.16 (4H, br s), 3.02 (2H, narrow
m), 2.74 (2H, t, J ) 6.3 Hz), 2.65 (2H, br t, J ) 6.8 Hz), 1.80
(2H, apparent pentet, J ) 6.4 Hz), 1.30 (6H, s); NOE data 7.16
(3.02, 9%; 2.74, 4%), 3.02 (7.16, 24%; 1.30, 7%), 1.30 (3.02, 10%);
13C NMR δ 179.8 (0), 142.2 (0), 139.4 (0), 133.5 (0), 128.5 (1),
126.32 (1), 126.28 (1), 125.5 (1), 114.7 (0), 41.9 (2), 40.1 (0), 30.4
(2), 25.2 (2), 24.8 (2C, 3), 22.7 (2). Minor isomer 22b (discernible
signals from spectrum of mixture): 1H NMR δ 8.07 (1H, br d, J
) 7.5 Hz), 2.85 (2H, m), 2.79 (2H, t, J ) 6.2 Hz), 2.36 (2H, br t,
J ) 6.4 Hz), 1.86 (2H, apparent pentet, J ) 6.3 Hz), 1.36 (6H,
s).
1′,2′,3′,4′-Tetr a h yd r o-4,4-d im eth yl-4-oxa sp ir o[cyclop en -
ta n e-2,1′-n a p h th a len e]-1,3-d ion e (23). Tan-colored resin; 1H
NMR δ 7.18 (1H, ddd, J ) 1.7, 7.2, 8.3 Hz), 6.90 (1H, dd, J )
1.2, 8.4 Hz), 6.84 (1H, apparent dt, J ) 1.3, 7.5 Hz), 6.55 (1H,
dd, J ) 1.6, 7.8 Hz), 4.34 (2H, m), 2.95 (1H, d, J ) 18.1 Hz),
2.80 (1H, d, J ) 18.2 Hz), 2.11 (2H, m), 1.41 (3H, s), 1.38 (3H,
s); 13C NMR δ 220.6 (0), 215.0 (0), 156.1 (0), 135.9 (0), 129.6 (1),
128.6 (1), 121.1 (1), 117.9 (1), 59.9 (2), 56.2 (0), 49.7 (2), 45.5 (0),
29.0 (2), 24.9 (3), 23.9 (3).
3,4-Dih yd r o-3,3-d im eth yl-5-(d ip h en ylm eth ylen e)-2-fu r a -
n on e (26). Pale yellow solid, mp 111-113 °C; 1H NMR δ 7.40-
7.17 (10H, m), 2.77 (2H, s), 1.33 (6H, s); 13C NMR δ 179.9 (0),
144.1 (0), 138.8 (0), 137.5 (0), 130.0 (1), 129.4 (1), 128.5 (1), 128.0
(1), 127.2 (1), 126.9 (1), 119.3 (0), 41.6 (2), 39.8 (0), 24.7 (2C, 3).
(1′R*,2S*)- (28) a n d (1′R*,2R*)-4,4-Dim eth yl-2-h yd r oxy-
2-(1-h yd r oxy-1-p h en yleth yl)cyclobu ta n on e (29). A solution
of acetophenone (0.41 g, 3.4 mmol) in CH2Cl2 (10 mL) was cooled
to -78 °C before BF3‚Et2O (0.42 mL, 3.4 mmol) and 3 (0.97 g,
3.7 mmol) were added. The temperature was raised to -20 °C,
and the mixture was stirred for 29 h. The mixture was poured
into H2O, and the aqueous layer was extracted with CH2Cl2. The
combined organic extracts were dried over anhydrous Na2SO4
and concentrated under vacuum to give a yellow viscous oil (0.76
g) composed of acetophenone, 28, 19, and 29 in a ratio of 11:
1
5.7:3.4:1 by H NMR. Flash chromatography using an increas-
ing proportion of EtOAc in hexanes provided 28 (167 mg, 21%)
and 29 (29 mg, 4%). Major diastereomer 28: white solid, mp
79.5-80.5 °C; 1H NMR (CD3OD) δ 7.45 (2H, d, J ) 7.1 Hz), 7.29
(2H, apparent t, J ) 7.4 Hz), 7.21 (1H, apparent t, J ) 7.0 Hz),
2.35 (1H, d, J ) 12.5 Hz), 1.72 (1H, d, J ) 12.5 Hz), 1.64 (3H,
s), 1.18 (3H, s), 0.51 (3H, s); 13C NMR (CD3OD) δ 219.7 (0), 145.8
(0), 128.8 (2C, 1), 128.4 (2C, 1), 128.0 (1), 94.6 (0), 76.1 (0), 55.2
(0), 40.5 (2), 25.5 (3), 25.0 (3), 20.8 (3). Minor diastereomer 29:
white solid, mp 150-151.5 °C; 1H NMR (CD3OD) δ 7.57 (2H, d,
J ) 7.2 Hz), 7.29 (2H, apparent t, J ) 7.4 Hz), 7.20 (1H, apparent
t, J ) 7.2 Hz), 2.33 (1H, d, J ) 12.5 Hz), 1.67 (3H, s), 1.47 (1H,
d, J ) 12.5 Hz), 1.21 (3H, s), 1.02 (3H, s); 13C NMR (CD3OD) δ
221.0 (0), 146.4 (0), 128.6 (2C, 1), 128.0 (2C, 1), 127.9 (1), 94.0
(0), 76.0 (0), 55.1 (0), 40.6 (2), 25.4 (3), 24.5 (3), 21.2 (3). The
relative stereochemistry of 29 was determined by X-ray crystal-
lography.12
3,4-Dih yd r o-3,3-d im et h yl-5-(1-(1,2,3,4-t et r a h yd r o-4-ox-
a n a p h th ylid en e))-2-fu r a n on e (24a ,b). Major isomer 24a :
white solid, mp 164-165 °C; 1H NMR δ 7.14 (2H, m), 6.89 (2H,
m), 4.23 (2H, t, J ) 5.7 Hz), 3.08 (2H, br s), 2.80 (2H, br t, J )
5.7 Hz), 1.35 (6H, s); NOE data 3.08 (d, J ) 7.3 Hz, at δ 7.15,
23%; 1.35, 7%), 1.35 (3.08, 10%); 13C NMR δ 179.3 (0), 154.6 (0),
141.1 (0), 128.19 (1), 126.2 (1), 120.2 (1), 120.1 (0), 117.3 (1),
109.0 (0), 66.2 (2), 41.7 (2), 40.0 (0), 25.1 (2C, 3), 24.5 (2). Minor
isomer 24b (discernible signals from spectra of mixture): 1H
NMR δ 8.09 (1H, dd, J ) 1.6, 8.1 Hz), 2.85 (2H, br s), 2.52 (2H,
apparent t, J ) 5.6 Hz), 1.37 (6H, s); 13C NMR δ 153.7 (0), 140.3
(0), 129.2 (1), 128.24 (1), 120.9 (1), 116.9 (1), 65.6 (2), 40.3 (2),
26.2 (2), 25.2 (2C, 3).
Ack n ow led gm en t. We are grateful to Dr. J ohn N.
Bridson of this Department for the X-ray crystal struc-
ture. This work was supported by a grant from the
Natural Sciences and Engineering Research Council of
Canada.
Su p p or tin g In for m a tion Ava ila ble: Reaction conditions
1
and additional charaterization data (UV, IR, MS, HRMS), H
and 13C NMR spectra for products, and X-ray structure report
for 29 (80 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.
4,4-Dim et h yl-2,2-d ip h en ylcyclop en t a n e-1,3-d ion e (25).
White solid, mp 67-68 °C; 1H NMR δ 7.40-7.23 (6H, m), 7.15-
7.03 (4H, m), 2.78 (2H, s), 1.39 (6H, s); 13C NMR δ 216.4 (0),
211.2 (0), 137.4 (2C, 0), 128.7 (1), 127.8 (1), 51.3 (2), 47.3 (0),
26.1 (2C, 3).
J O971867R