Diels-Alder Reactions of Cyclopentadienones
resulting solution was concentrated in vacuo, and the product was
purified by flash chromatography (Hex/EA 80:20).
Compound 6g. The product was obtained as a white solid
(0.0021 g, 25%): mp 155-156 °C; TLC Rf ) 0.40 (Hex/EA 2:1);
1H NMR (400 MHz, CDCl3) δ 7.06 (s, 1H), 6.87 (s, 2H), 5.04 (s,
2H), 4.94 (s, 2H), 2.33 (s, 3H), 1.89 (s, 6H), 0.34 (s, 9H), -0.02
(s, 9H); 13C NMR (100 MHz, CDCl3) δ147.0, 146.0, 143.7, 142.4,
141.3, 140.0, 136.5, 136.4, 136.0, 127.8, 63.4, 62.9, 21.1, 21.0,
2.3, 0.8; HRMS (FAB) calcd for M+ - OH (C23H35OSi2) 383.2227,
found 383.2216.
Compound 6h. The product was obtained as a white solid
(0.0029 g, 38%): mp 123-126 °C; TLC Rf ) 0.33 (Hex/EA 2:1);
1H NMR (400 MHz, CDCl3) δ 7.36-7.31 (2H), 7.06 (d, J ) 7.6
Hz, 1H), 6.97 (t, J ) 7.6 Hz, 1H), 6.92 (d, J ) 8.0 Hz, 1H), 5.01
(s, 2H), 4.93 (s, 2H), 3.76 (s, 3H), 0.38 (s, 9H), 0.02 (s, 9H); 13C
NMR (100 MHz, CDCl3) δ 156.8, 145.7, 145.1, 144.1, 141.2, 137.5,
133.8, 131.6, 128.8, 120.1, 110.4, 109.8, 63.3, 63.2, 55.1, 2.4, 0.7;
HRMS (FAB) calcd for M+ - CH3 (C20H29O3Si2) 373.1656, found
373.1659.
Compound 6i. The product was obtained as a white solid (0.0033
g, 40%): TLC Rf ) 0.30 (Hex/EA 2:1); mp 175-177 °C; 1H NMR
(400 MHz, CDCl3) δ 8.13 (br, 1H), 7.64 (d, J ) 8 Hz, 1H), 7.50
(s, 1H), 7.19-7.17 (t, J ) 3.0 Hz, 1H), 7.14 (dd, J ) 8, 7.0 Hz,
1H), 6.98 (d, J ) 7.0 Hz, 1H), 6.61 (dd, J ) 3.0, 2 Hz, 1H), 5.03
(s, 2H), 4.97 (q, J ) 10.4 Hz, 2H), 0.37 (s, 9H), -0.15 (s, 9H);
13C NMR (100 MHz, CDCl3) δ 146.4, 145.0, 144.5, 142.3, 141.6,
136.8, 135.4, 128.6, 127.6, 124.2, 122.8, 119.9, 119.7, 103.8, 63.2,
63.1, 2.4, 0.7; HRMS (FAB) calcd for M+ (C22H31NO2Si2)
397.1893, found 397.1884.
Compound 6j. The product was obtained as a white solid
(0.0040 g, 38%): mp 165-166 °C; TLC Rf ) 0.48 (Hex/EA 2:1);
1H NMR (400 MHz, CDCl3) δ 7.56-7.53 (2H), 7.23-7.19 (2H),
6.99 (dd, J ) 7.6, 1.2 Hz, 1H), 6.61 (d, J ) 3.6 Hz, 1H), 5.05 (s,
2H), 4.92 (d, J ) 1.2 Hz, 2H), 1.30 (s, 9H), 0.30 (s, 9H), -0.00 (s,
9H); 13C NMR (100 MHz, CDCl3) δ 148.7, 148.2, 145.9, 143.4,
140.5, 139.7, 135.4, 132.2, 131.9, 128.5, 128.1, 122.1, 120.0, 106.7,
99.5, 83.0, 63.4, 63.3, 27.8, 2.8, 0.6; HRMS (FAB) calcd for M+
- OH (C27H38NO3Si2) 480.2391, found 480.2371.
Compound 6a. The product was obtained as a light yellow solid
(0.0074 g, 88%): mp 151-153 °C; TLC Rf ) 0.30 (Hex/EA 2:1);
1H NMR (400 MHz, CDCl3) δ 7.94 (d, J ) 7.4 Hz, 1H), 7.60-7.49
(2H), 7.27 (d, J ) 7.4 Hz, 1H), 7.07 (s, 1H), 5.04 (s, 2H), 4.93
(ABq, J ) 12.4 Hz, 2H), 3.14 (br s, 2H), 0.33 (s, 9H), 0.05 (s,
9H); 13C NMR (100 MHz, CDCl3) δ 148.9, 146.2, 144.8, 143.7,
141.8, 140.1, 139.7, 135.0, 132.9, 131.9, 128.4, 124.0, 63.2, 62.9,
2.5, 0.5; HRMS (FAB) calcd for M+ - OH (C20H28O3NSi2)
386.1608, found 386.1572.
Compound 6b. The product was obtained as a pale yellow solid
(0.0054 g, 62%): mp 156-158 °C; TLC Rf ) 0.30 (Hex/EA 2:1);
1H NMR (400 MHz, CDCl3) δ 8.06 (d, J ) 8.6 Hz, 2H), 7.35 (d,
J ) 8.6 Hz, 2H), 7.31 (s, 1H), 5.02 (s, 2H), 4.94 (s, 2H), 3,95 (s,
3H), 0.38 (s, 9H), 0.03 (s, 9H); 13C NMR (100 MHz, CDCl3) δ
167.0, 150.0, 148.3, 146.4, 144.6, 141.9, 140.3, 136.3, 129.6, 129.3,
128.9, 63.3, 63.1, 52.2, 3.0, 0.6; HRMS (FAB) calcd for
MH+(C22H33O4Si2) 417.1917, found 417.1914.
Compound 6c. The product was obtained as a pale yellow solid
(0.0056 g, 65%): mp 160-161 °C; TLC Rf ) 0.30 (Hex/EA 2:1);
1H NMR (400 MHz, CDCl3) δ 7.88 (dd, J ) 7.6, 1.6 Hz, 1H),
7.50-7.40 (m, 2H), 7.18 (dd, J ) 7.6, 1.6 Hz, 1H), 7.10 (s, 1H),
5.03 (s, 2H), 4.92 (ABq, J ) 12.4 Hz, 2H), 3.62 (s, 3H), 0.33 (s,
9H), 0.00 (s, 9H); 13C NMR (100 MHz, CDCl3) δ 168.0, 147.9,
145.8, 145.7, 143.9, 141.0, 139.6, 135.8, 131.8, 130.8, 130, 6, 129.7,
127.3, 63.3, 63.1, 51.9, 2.5, 0.6; HRMS (FAB) calcd for M+
OH (C22H31O3Si2) 399.1812, found 399.1796.
-
Compound 6d. The product was obtained as a light yellow solid
(0.0037 g, 50%): mp 80-81 °C; TLC Rf ) 0.35 (Hex/EA 2:1); 1H
NMR (400 MHz, CDCl3) δ 7.38-7.36 (4H), 7.28-7.26 (2H), 5.02
(s, 2H), 4.94 (s, 2H), 0.38 (s, 9H), 0.03 (s, 9H); 13C NMR (100
MHz, CDCl3) δ 149.4, 146.2, 145.3, 144.1, 141.7, 140.4, 136.7,
129.5, 128.0, 127.2, 63.4, 63.1, 2.9, 0.6; HRMS (FAB) calcd for
M+ - OH (C20H29OSi2) 341.1757, found 341.1748.
Compound 6e. The product was obtained as a white solid
(0.0029 g, 32%): mp 142-145 °C; TLC Rf ) 0.40 (Hex/EA 2:1);
1H NMR (400 MHz, CDCl3) δ 7.37 (1H), 7.18-7.17 (4H), 5.01
(s, 2H), 4.93 (s, 2H), 3.14 (br, s, 2H), 2.63 (t, J ) 7.6 Hz, 2H),
1.64-1.56 (2H), 1.19-1.14 (2H), 0.95 (t, J ) 7.2 Hz, 3H), 0.37
(s, 9H), 0.03 (s, 9H); 13C NMR (100 MHz, CDCl3) δ 149.5, 146.2,
143.9, 142.6, 142.0, 141.6, 140.5, 136.7, 129.3, 128.0, 63.4, 63.1,
35.3, 33.7, 22.3, 14.0, 2.9. 0.6; HRMS (FAB) calcd for M+ - CH5O
(C23H33OSi2) 381.2071, found 381.2072.
Compound 6k. The product was obtained as a white solid
(0.0021 g, 28%): mp 159-161 °C; TLC Rf ) 0.33 (Hex/EA 2:1);
1H NMR (400 MHz, CDCl3) δ 8.63 (d, J ) 4.4 Hz, 1H), 7.76 (dt,
J ) 8.0, 2.0 Hz, 1H), 7.47-7.45 (m, 2H), 7.30-7.27 (m, 1H), 4.97
(s, 2H), 4.86 (s, 2H), 3.58 (br, 2H), 0.37 (s, 9H), 0.03 (s, 9H); 13
C
NMR (100 MHz, CDCl3) δ 162.8, 148.7, 147.9, 146.5, 145.4, 141.8,
141.0, 136.5, 135.9, 123.7, 122.1, 63.4, 63.0, 2.5, 0.5; HRMS (FAB)
calcd for MH+ (C19H29NO2Si2) 360.1815, found, 360.1824.
Compound 6f. The product was obtained as a white solid
(0.0047 g, 58%): TLC Rf ) 0.45 (Hex/EA 2:1); mp 138-139 °C;
1H NMR (400 MHz, CDCl3) δ 7.90-7.85 (2H), 7.56 (d, J ) 8.4
Hz, 1H), 7.50-7.46 (2H), 7.41-7.37 (2H), 7.28-7.25 (1H), 5.08
(s, 2H), 5.00 (s, 2H), 0.35 (s, 9H), -0.19 (s, 9H); 13C NMR (100
MHz, CDCl3) δ 146.7, 145.9, 144.4, 142.7, 141.6, 141.5, 137.6,
133.4, 133.2, 128.1, 127.6, 127.3, 126.6, 126.0, 125.8, 125.0, 63.3,
63.1, 2.5, 0.7; HRMS (FAB) calcd for M+ - OH (C24H31OSi2)
391.1913, found 391.1846.
Acknowledgment. We are grateful to Case Western Reserve
University and the National Science Foundation (CHE-0449642
and CHE-0743234) for financial support of this research.
Supporting Information Available: Copies of NMR spectra
for all new compounds. This material is available free of charge
JO900559N
J. Org. Chem. Vol. 74, No. 11, 2009 4245