Stereoselective Generation of E- and Z-Disubstituted Amide Enolates. Reductive Enolate Formation from Bicyclic Thioglycolate Lactams

A Fluorous, Pummerer Cyclative‐Capture Strategy for the Synthesis of N‐Heterocycles

“…Oxindoles (entries 1-7), tetrahydroisoquinolinones (entries 8-10) and tetrahydrobenzazepinones (entries [11][12][13][14][15][16][17] can be prepared by straightforward variation of the glyoxamide substrate. For the formation of six and seven-membered heterocycles (entries 8-17), electronic activation of the aromatic ring leads to higher yields of product.…”

“…A number of electrontransfer reagents are known to reduce a-heteroatom-substituted carbonyl compounds to the parent carbonyl compound. [14] By using a range of model tagged substrates, it was found that reduction with SmI 2 [15] resulted in the clean removal of the fluorous tag ( Figure 1). We have previously utilised this process in the cleavage of oxygen and sulfurlinker systems for solid-phase synthesis.…”

Reductive Lithiation and Multilithiated Compounds in Synthesis

“…Interestingly, the proposed model of stereoselective enolate generation assumes that no significant rotation occurs about the carbonyl-carbon/α-carbon bond during the two-electron reduction process (Scheme 12.5 In agreement with these hypotheses, good level of stereocontrol was observed in the formation of silyl enol ethers obtained from compounds 17, while poorer results were obtained with similar bicyclic thioglycolate lactams with less favorable O-C-C-S dihedral angles [22].…”

Aldol Reactions

“…The lithium enolate obtained by the method of Gleason et al [7] (Schemes 3.5 and 3.10) can be easily transmetallated with various boron species. The effect on the syn/anti selectivity and the diastereomeric excess (de) (two diastereomeric syn-57 and two diastereomeric anti-58 products are possible owing to the already existing stereocenter in the enolate) of the aldol reactions is summarized in Table 3.7 [22].…”

“…Therefore, some special strategies for the synthesis of enolates with defined E/Z configuration were developed, for example the two-electron reduction of thioglycolate lactams 19 (Scheme 3.5) [7].…”