A New Route to Enol Ethers

Abstract

Dithioorthoformates having various alkoxy groups were obtained by copper(II) bromide-promoted oxidative coupling of bis(phenylthio)methyltributylstannane with alcohols. The dithioorthoformates thus prepared are useful precursors for alkoxymethylidene complexes of titanium, which transform carbonyl compounds into a variety of enol ethers. Even the alkoxymethylidene complexes having a terminal olefin moiety can be prepared and employed for carbonyl olefination without formation of ring-closing metathesis product.

carbene complexes - esters - ketones - olefination - titanium

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Titanocene alkoxymethylidenes are also unreactive toward intermolecular reaction with olefins. Thus the treatment of dithioorthoformate 2a with 3 in the presence of 4-phenyl-but-1-ene gave the olefin metathesis product, 1-benzyloxy-4-phenyl-but-1-ene, in only less than 8% yield.

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