The synthesis of R-3-alkoxy-1-(1′-hydroxyethyl)-4-methoxy-2-(1"-propenyl)benzenes utilizing Corey-Bakshi-Shibata asymmetric reductions

Pyrolysis of the 3-O-allyl derivative 7 of isovanillin followed by alkylation of the derived allylphenol 8 afforded a series of benzaldehyde derivatives 9-11 each of which was transformed by initial treatment with methylmagnesium bromide followed by oxidation of the corresponding alcohols with activated manganese dioxide into a series of ketones 15-17. Palladium(0) catalysed isomerization of the double bond in the prop-2'-enyl side-chain afforded ketones 36-38 which were subjected to the Corey-Bakshi-Shibata asymmetric reduction protocol to afford the R-3-alkoxy-1-(1'-hydroxyethyl)-4-methoxy-2-(1"-propenyl) benzenes 42-44 in yields of approximately 60% and with ee's of 75%. (C) 2003 Elsevier Science Ltd. All rights reserved.