Asymmetric michael additions of ester enolates to enantiomerically pure vinylic sulfoxides
作者:Gary H. Posner、Moshe Weitzberg、Terence G. Hamill、Edward Asirvatham、He Cun-heng、Jon Clardy
DOI:10.1016/s0040-4020(01)90581-2
日期:1986.1
donors to enantiomerically pure Michael acceptor cycloalkenone sulfoxides 1a and 1b and unsaturated lactone sulfoxides 3a and 3b. The level of asymmetric induction in some cases is extraordinarily high (95% e.e. of final 1,5-dicarbonyl products). Adduct ester lactones 5 and 6 can be converted easily into some synthetically versatile, trifunctional, 3-substituted glutarate esters of highenantiomeric purity
Asymmetric Michael Addition Reaction of Phosphorus-Stabilized Allyl Anions with Cyclic Enones
作者:Scott E. Denmark、Jung-Ho Kim
DOI:10.1021/jo00128a028
日期:1995.11
The asymmetric Michael addition reaction of chirally modified P-allyl anions derived from enantiomerically enriched 2-allyl-1,3,2-oxazaphosphorinane 2-oxides has been investigated with cyclic enones. The racemic 1,3,2-oxazaphosphorinane 2-oxide 3 has been shown to be extremely diastereoselective in the Michael addition to 5-, 6-, and 7-ring enones. With the enantiomerically enriched 2-allyl-1,3,2-oxazaphosphorinane 2-oxides, high regio- and diastereoselectivities (88-90% diastereomeric excess) have been achieved in the Michael addition reaction of one of the diastereomers (cis series). The Michael reaction of the anions derived from the trans series were not diastereoselective (similar to 10% diastereomeric excess). The origin of the addition selectivity can be rationalized by (1) consideration of the structure and conformational preferences of the allyl anion (parallel conformation, s-trans, no lithium contact), (2) conformational analysis of the 1,3,2-oxazaphosphorinane 2-oxide ring (chair, equatorial allyl group) and (3) assumption of a 10-membered ring transition state structure with lithium coordination of the enone.
Chiroptical studies of labile or difficult-to-resolve molecules generated by chiral laser photochemistry. 2. Products and steric course of the phototransformation of the racemate