Position and enantioselective dihydroxylation of 2-hydroxymethyl- and 2-hydroxyethyl-1,3-butadiene derivatives using bis-cinchona alkaloid catalysts
作者:Mark C. Noe、E.J. Corey
DOI:10.1016/0040-4039(96)00162-1
日期:1996.3
asymmetric dihydroxylation of p-methoxybenzoate esters of p-methoxyphenyl ethers of 2-hydroxymethyl-1,3-butadienes or 2-hydroxyethyl-1,3-butadienes proceeds with excellent position and enantioselectivityusingbis-cinchonaalkaloidcatalysts. The regioselectivity of these reactions is strongly influenced by binding interactions between the aromatic ether or ester group and the catalyst as predicted
A 3-step 100% atom economic sequence is reported whereby a variety of phenols react with 2 mol equiv. of allene to give phenoxymethyl-1,3-dienyl ethers. Subsequent thermal Claisen rearrangement to C-1,3-dienes and acid catalysed ring closure furnishes 3:1–6.5:1 mixtures of exo-methylene chromans and dihydrobenzofurans with the former predominating.