O-Silylated 2-Polyfluoroacyl-cycloalkanones
917
solutions on a Bruker DPX-200 spectrometer operating at 200.1 (1H), 50.3 (13C), and 188.3 (19F)
MHz. 2-Poly¯uoroacyl-cycloalkanones 1 [14], 2 [15, 16] and 5 [15] were prepared by a Claisen-type
condensation of cyclopentanone or cyclohexanone and alkylpoly¯uoroacylates in the presence of
sodium methylate in dry ether [15, 16].
General method for the synthesis of compounds 3 and 4
To a solution of 52 mmol 1,3-diketone and 100 mmol dry triethylamine (10.4 g) in 100 cm3 dry
diethyl ether, a solution of 52 mmol (6.7 g) freshly distilled dichlorodimethylsilane in 20 cm3 dry
diethyl ether was added within 0.5 h. After stirring for 16 h, triethylamine hydrochloride was ®ltered
off and washed with cold diethyl ether (2 Â 10 cm3). The solvent was removed, and the residue was
distilled in vacuo.
7-Per¯uoropropyl-1,2-dihydro-5,5-dimethyl-4,6-dioxa-5-silaindene (3; C11H11F7O2Si)
Yellow oil; yield: 63%; b.p.: 94±96ꢀC (20 torr); MS: m/z (%) 336 (M , 100), (M-C2F5 , 72), 167
(M-C3F7 , 38), and other fragments; HRMS: found 336.0409, calcd. 336.0417.
4-Tri¯uoromethyl-6,7-dihydro-2,2-dimethyl-5H-1,3-dioxa-2-silanaphthalene (4; C10H13F3O2Si)
Colorless liquid; yield: 77%; b.p.: 48±51ꢀC (0.8 torr, ®rst distillation), 41±44ꢀC (0.9 torr, second
distillation); MS: m/z (%) 250 (M , 100), 235 (M-Me , 62), 181 (M-CF3 , 70), 166
(M-Me-CF3 , 10), and other fragments; HRMS: found: 250.0633, calcd. 250.0637.
General method for the synthesis of compounds 6±8
To a solution of 8 mmol 1,3-diketone and 8 mmol (0.8 g) dry triethylamine in 10 cm3 dry diethyl
ether, a solution of 8 mmol (0.9 g) freshly distilled chlorotrimethylsilane in 5 cm3 dry diethyl ether
was added within 0.5 h. After stirring for 0.5 h, triethylamine hydrochloride was ®ltered off and
washed with cold diethyl ether (2 Â 5 cm3). The solvent was removed, and the residue was distilled
in vacuo. The products are yellowish liquids (compound 8 could not be isolated in pure state, but was
characterized by MS and NMR spectroscopy).
2-Per¯uorobutanoyl-1-trimethylsiloxycyclopentene (6; C12H15F7O2Si)
Yield: 79%; b.p.: 52±55ꢀC (1 torr); MS: m/z (%) 352 (M , 13), 337 (M-Me , 100), 183
(M-C3F7 , 45), 73 (Me3Si , 21), 15 (Me , 10), and other fragments; HRMS: found 352.0720,
calcd. 352.0730.
2-Tri¯uoroacetyl-1-trimethylsiloxycyclohexene (7; C11H17F3O2Si)
Yield: 63%; b.p.: 114±116ꢀC (10 torr); MS: m/z (%) 266 (M , 18), 251 (M-Me , 70), 197
(M-CF3 , 100), 169 (M-CF3CO , 6), 97 (CF3CO , 8), 73 (Me3Si , 76), 69 (CF3 , 10), and other
fragments; HRMS: found 266.0966, calcd. 266.0950.
2-Tri¯uoroacetyl-1-trimethylsiloxycyclopentene (8; C10H15F3O2Si)
Yield: 74%; b.p.: 50±51ꢀC (1 torr); MS: m/z (%) 252 (M , 12), 237 (M-Me , 100), 183
(M-CF3 , 32), 73 (Me3Si , 56), and other fragments.