Stereochemistry of p-chiral phosphinylacetic acid esters I asymmetric synthesis of substituted alkadiene-1,2-car☐ylic-1 and X-chiral α, β-unsaturated car☐ylic acid esters

Asymmetric Ylide Reactions: Epoxidation, Cyclopropanation, Aziridination, Olefination, and Rearrangement

“…The idea of differentiating two enantiomers of a carbonyl compound, which contains one or more stereogenic centers adjacent to the carbonyl group, is readily apparent and easier to achieve than other asymmetric applications of the ylide olefination reaction. The first such attempt appeared as early as 1975 . When racemic α-phenylcyclohexanone 422 was treated with the anion of chiral phosphinate ester ( S )-(−)- 423 , the olefination product (−)- 424 was obtained.…”

“…Such an idea was attempted at the beginning of the 1960s. Several attempts ,− have been well documented. However, the early attempts had limited success and only low ee values were reported.…”

“…The first such attempt appeared as early as 1975. 172 When racemic R-phenylcyclohexanone 422 was treated with the anion of chiral phosphinate ester (S)-(-)-423, the olefination product (-)-424 was obtained. The optically active starting ketone (S)-(-)-422 was also recovered in 4.8% optical purity (Scheme 114).…”

Electrophilic addition to allenic derivatives: selectivity, regio- and stereochemistry and mechanisms

“…This happens when rotation and bending of a,13ethylenic cation is more rapid than nucleophilic attack that could be slowed by steric hindrance. A loss of proton may also occur from an adjacent methyl group of this entity giving a conjugated diene (eq 50). Minor Major -rJ,r'3 strongly electron-donating auisei cue/its such as Pb, OEt, Me and R3 electron-withdrawing *ul>*tituenc CH^OR or alJcyl group ; "electrophiles with poor bridging ability MX, R^CX, ClT hen it was shown that hydrochlorination of phenylallene (eq 4) and ethoxyallene (entry 27 of Table I) follows a stepwise process in which rate-determining proton transfer on the /3-carbon leads to a transition state resembling the perpendicular a-vinylbenzyl and a-vinylethoxy cation.…”

“…This product is formed exclusively in methanol (entry 53). a-Ketols 209, 13lactone 210, and 7-enones 211 are formed without participation, the former being obtained through the spiro dioxide of allene 207 (path 1 of Figure 13) (entries [50][51][52][53][54][55][56].…”