New horizons in carbonyl chemistry: reagents for nucleophilic acylation

Preparation of 3-acetamido-2,5-dihydrothiophenes

“…While the mechanism of this reaction has not been investigated in detail, the isolation of compounds 5 and 6 suggests a sequence of intermediates as shown by 2-4 in Scheme I leading to 7. The first step would be formation of a mixed anhydride 2 followed by ring closure to an oxazolone 3.…”

“…3 In the course of our study on DAMN derivatives, we have observed that DAMN Schiff bases 2 were more resistant than DAMN itself toward degradation reactions under several conditions. Oxidation of 2 with reagents, such as DISN and dichlorodicyanobenzoquinone (DDQ), is known to afford 2substituted imidazole-4,5-dicarbonitrile.6 The potential utility of nitrile reactions of the open-chain DAMN derivatives for synthesis of a wide variety of heterocyclic compounds has prompted us to study the nitrile hydration reaction of a series of Schiff bases 2a-g.3b 7 Reactions. Preliminary examination of 2 showed that they underwent preferential cleavages of the azomethine linkages upon heating with acid or base.…”

Generation and reactivity of α-metalated vinyl ethers

“…Baldwin et al demonstrated 5 that MVE (7) is metalated in the α position by the addition of t-BuLi in pentane to a cold (Ϫ65 ЊC) solution of excess MVE (1.6 equiv. with respect to t-BuLi) in THF (∼1.4 M) followed by slow warming to 0 ЊC (Scheme 2).…”

New silicon-phosphorus reagents in organic synthesis. Carbonyl and conjugate addition reactions of silicon phosphite esters and related systems

“…Four silicon-phosphorus reagents were prepared for examination for insertion reactions in carbonyl substrates. Dimethyl trimethylsilyl phosphite17 (10) and dimethyl triethylsilyl phosphite17 (11) were prepared by a variation of known procedures. [19][20] Dimethyl ferf-butyldimethylsilyl phosphite (16) was prepared analogously from dimethyl phosphite and feri-butyldimethylchlorosilane.…”