A cerium(III) modification of the Peterson reaction: methylenation of readily enolizable carbonyl compounds

Abstract

of 1, 2, and 3 is consistent with a common mechanism being followed in each case. Whatever the nature of the mechanism, a quinone methide intermediate cannot be formed from 2 because of the meta relationship of its substituents. RegistryNo. 1,623-052; 2,62&24-6; 3,49800-0; nitrobenzene, 98-95-3; lignin, 9005-53-2. (16) Leopold, B. Acta Chem. Scand. 1950, 4 , 1523. (17) Schultz, T. P.; Chen, C. I.; Goldstein, I. S.; Scaringelli, F. P. J.

Branching cascades provide access to two amino-oxazoline compound libraries

“…12 Therefore, we resorted to Peterson olefination using trimethylsilyl methyl lithium that provided the desired olefin 6, however, along with major amount of desilylated olefin 7 (Scheme 3a). 13 To avoid the silyl deprotection during Peterson olefination (Scheme 3a), the hydroxyl group in phenolic ketones 4 was protected as p-methoxybenzyl (PMB) ether in very good yield by treating with 4-methoxybenzyl chloride in the presence of potassium carbonate. 14 The ketones 8a-c were converted into the corresponding olefin 9a-c in good yields by using trimethylsilyl methyl lithium (Scheme 3b).…”

“…The crude compound was purified by flash column chromatography on silica gel (230-400 mesh) using MeOH/CH 2 Cl 2 (2-5%; MeOH buffered with NH 3 10:1) as a gradient to afford compound 23b (0.2 g, 57%) as a colourless viscous liquid. 1 13 To a solution of methyltriphenylphosphonium bromide (1.6 equiv) in dry THF (100 mL), KO t Bu (1.75 equiv in 75 mL dry THF) was added dropwise at 0°C under a N 2 atmosphere and stirred for 2 h at 0°C. The respective ketone 7a-g (5.0 g, 1 equiv) in dry THF (50 mL) was added dropwise at 0°C and refluxed for 5 h. After completion of the reaction, water (150 mL) was added and the reaction mixture was extracted with EtOAc (3 Â 200 mL).…”

“…1 Hz, 3H) 13. C NMR (101 MHz, CDCl 3 ): d 159.4, 156.1, 149.ESI) m/z calcd for C 25 H 26 NO 4 [M+H] + : 404.19, found: 404.…”

“…) 13. C NMR (101 MHz, CDC 3 ): d 197.3, 175.3, 175.2, 167.6, 165.0, 156.7, 154.3, 154.3, 136.3, 136.1, 135.6, 135.6, 132.1, 131.7, 125.7, 125.7, 123.4, 119.0, 118.9, 118.1, 118.1, 62.9, 62.9, 52.6, 52.5, 43.0, 38.7, 32.3, 32.2, 26.1, 26.0, 21.1, 21.0, 20.6, 20.2, 18.4, 18.4, À5.2, À5.2.…”

Trimethylsilylmethyllithium

“…The use of the lithium agent (1) gives superior yields compared to the use of Trimethylsilylmethylmagnesium Chloride with cerium. 11 …”