Alkyl vinyl ketones, Michael reactions, aldehydes

Scheme 2.20 Enantioselective intermolecular Michael reaction between aldehydes and alkyl vinyl ketones.

Alkylation. Cyclopropane formation is observed in the reaction of aldehydes with dimethyl 2,3-dihalopropanoate in the presence of Et2NSiMc3. This process is a modification of the Michael reaction between aldehydes and methyl vinyl ketone that leads to -ketoaldehydes. ... 

In 2008, Chi et al. reported a tandem reaction of indoles, a,P-unsaturated aldehydes, and methyl vinyl ketone (MVK) for the synthesis of chiral indole derivatives with two stereogenic centers [ 19]. To avoid the interference of the two secondary amine catalysts and cocatalyst acid, the soluble star polymer-based site isolatbn method was adopted, whereby the supported imidazolidinone catalyst promoted initial Friedel-Crafts alkylation and the supported pyrrolidine derivative promoted the following Michael addition to MVK (Scheme 9.19). Notably, simple combination of these catalysts in one pot didn t mediate the cascade reaction efficiently despite the fact that the MacMillan imidazolidinone and pyrrolidine catalyst can efficiently promote separate Friedel-Crafts reaction and Michael addition, respectively. Moreover, when the pyrrolidine catalyst was replaced by its enantiomer, a diaste-reomer of the product could be obtained with high enantioselectivity. This smdy presented a novel solution to the efficient combination of incompatible substrates and catalysts. 

P-Alkylation. The Michael-Arbuzov reaction of chloromethyl p-tolyl sulfide with trimethyl Phosphite or triethyl phosphite yields dimethyl- or diethylphosphonylmethyl p-tolyl sulfides, which are important intermediates for the synthesis of vinyl sulfides and sulfoxides, as well as for optically active derivatives of dimethylphosphonylmethyl p-tolyl sulfoxide (eq 7). This method of preparation of the chiral p-tolylthio monosulfoxide is complementary to the reaction using dimethylphosphonyl-methyllithium and (—)-(5)-menthyl p-toluenesulfinate in which the (+)-(7 isomer is obtained in high 3ueld and high optical purity (eq 8). The lithio dimethylphosphonylmethyl p-tolyl sulfoxide reacts with aldehydes and ketones to give the corresponding vinyl sulfoxides, which can be converted into optically active allylic alcohols (eq 9). ... 

A condensation of vinyl sulphides of synthetic value involves the reaction of a-ethylthio-styrenes with an aldehyde in the presence of a Lewis acid catalyst to give 3-ethylthio-indenes. Regiospecific and stereospecific pentannelation i.e, fusion of a cyclopentane ring) of an alicyclic ketone involves arylthiomethylen-ation followed by base-catalysed addition to an aj8-unsaturated ester. a-Phenyl-thiobutenolides are less reactive Michael acceptors than their sulphoxide counterparts, and /SjS-dichlorovinyl sulphides are less reactive in electrophilic reactions than their oxygen counterparts. Dimerization of aryl a-cyanovinyl sulphides occurs more readily than that of alkyl analogues, since the intermediate 1,4-diradical ArSC(CN)CH2CH2d(CN)SAr, which cyclizes to the cyclobutane, is more stable. Products obtained by photolysis of methyl vinyl sulphide are accounted for by homolysis of both vinyl—S and methyl—S bonds. The kinetics of catalysed cis-trans isomerization of aryl vinyl sulphides have been studied. ... 

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