Acylvinyl and Vinylogous Synthons

Five- and six–membered cyclic α-acylvinyl anionic synthons: synthesis of α-trimethylsilyl-α,β-unsaturated cycloalkenones and their conversion into 2-(hydroxydimethylsilyl)cycloalk-2-enones through carbon–silicon bond scission

“…The compounds are cyclic α-acylvinyl anionic synthons. 2 There are only a few reports for preparation of cyclic α-or β-acylvinyl anionic synthons. The synthons bearing either the silyl-or the stannyl-3 group act as a masking agent for the anions.…”

A Soft Vinyl Enolization Approach to α‐Acylvinyl Anions: Direct Aldol/Aldol Condensation Reactions of (E)‐β‐Chlorovinyl Ketones

“…[4] Moreover, the presence of other C(sp 2 /sp 3 ) À H bonds in conjugated carbonyl compounds under strong basic conditions adds more complexity to the degree of chemocontrol. [5] Although alternative synthetic methods to form allenolates from alkynyl carbonyl compounds have been developed to avoid such regio-and chemoselectivity issues, [6][7][8][9] new methods for the direct generation of allenol/allenolates from a,b-unsaturated carbonyl compounds are highly desirable for the development of a-acylvinyl nucleophile equivalents.…”

“…The non-planar conformational preference of (E)-b-chlorovinyl ketones, as opposed to the planar conformational preference of (Z)-b-chlorovinyl ketones, was believed to result in better orbital overlap between the p C-O bonding orbital and the s * aÀ CÀH anti-bonding orbital, thus allowing for a mild a-vinyl enolization of (E)-b-chlorovinyl ketones (Scheme 2). Motivated by our earlier studies combined with the lack of access to a-vinyl nucleophilic synthons from a,bunsaturated carbonyl compounds under mild reaction conditions, [5] we examined the a-vinyl enolization of (E)-bchlorovinyl ketones for intermolecular C À C bond formations. Herein, we describe the realization of such direct and mild CÀC bond formations in the context of aldol and aldol condensation reactions through a facile vinyl enolization method.…”

Selective Synthesis of Unsymmetrical 3,4-Disubstituted and 4-Substituted 2(5H)-Furanones

“…19 We have also shown that monobromo derivatives 6 are useful precursors to unsymmetrical 3,4-disubstituted 2(5H)-furanones as well as to 4-aryl-2(5H)-furanones. Thus, compound 4 has been used as an equivalent of a cyclic a-bromo substituted b-acylvinyl cationic synthon.…”