Dimerization of Silyl Ketene Acetal: Effect of Lewis Acid Selection on Product Yield and Structure

Dependence of the Reactivities of Titanium Enolates on How They Are Generated: Diastereoselective Coupling of Phenylacetic Acid Esters Using Titanium Tetrachloride

“…Using these data, we attempted to compare the selectivities of methods i, ii, and iii. However, the homocoupling of 5a by method i has not been reported, and the stereoselectivity of the homocoupling of 5a by method ii has not been described 3a. Thus, we attempted the coupling of 5a by method i and reexamined the reaction by method ii.…”

“…Oxidative Coupling of 5a and 5c by Methods i and ii. Oxidative coupling by methods i and ii was carried out by the procedures described in the literature. ,3a …”

“…Titanium enolates 1 , which are useful intermediates for carbon−carbon bond formation, can be generated from carbonyl compounds 2 by three methods (Scheme ): (i) transmetalation of lithium enolates 3 , which can be prepared from 2 , (ii) transmetalation of silyl enol ethers 4 , which can be prepared from 3 , and (iii) direct generation from 2 , when 2 are enolizable amides and carbonyl compounds . These three methods give formally identical titanium enolates 1 , but it is not yet clear if the reactivities of 1 depend on how they are generated.…”