| Title: | Direct aldehyde homologation utilized to construct a conjugated-tetraene hydrocarbon insect pheromone |
| Address: | "Crop Bioprotection Research Unit, National Center for Agricultural Utilization Research, Agricultural Research Service, U.S. Department of Agriculture, 1815 North University Street, Peoria, Illinois 61604, USA. petrosrj@ncaur,usda.gov" |
| ISSN/ISBN: | 0021-8561 (Print) 0021-8561 (Linking) |
| Abstract: | "New phosphonate reagents were developed for the two-carbon homologation of aldehydes to methyl- or ethyl-branched unsaturated aldehydes and used in the practical synthesis of (2E,4E,6E,8E)-3,5-dimethyl-7-ethyl-2,4,6,8-undecatetraene (1), a pheromone of the beetle Carpophilus lugubris. The phosphonate reagents, diethyl ethylformyl-2-phosphonate dimethylhydrazone and diethyl 1-propylformyl-2-phosphonate dimethylhydrazone, contained a protected aldehyde group instead of the usual ester group. A homologation cycle entailed condensation of the reagent with the starting aldehyde, followed by removal of the dimethylhydrazone protective group with a biphasic mixture of dilute HCl and petroleum ether. This robust two-step process replaces the standard three-step aldehyde homologation route using ester-based Horner-Wadsworth-Emmons reagents. The new synthesis of compound 1 from (2E)-2-methyl-2-butenal was run on a 10-g scale and required just five steps (two cycles of condensation and deprotection, followed by a final Wittig olefination) instead of the usual seven. In addition, the Wittig olefination step was simplified and its E-isomer selectivity was improved. The overall yield for the entire synthetic pathway was increased from 20% to 37%, enhancing the commercial potential of Carpophilus pheromones" |
| Keywords: | Aldehydes/chemical synthesis/*chemistry Alkenes/chemical synthesis Animals Coleoptera/*chemistry Indicators and Reagents Organophosphonates Pheromones/*chemical synthesis; |
| Notes: | "MedlinePetroski, Richard J Bartelt, Robert J eng 2007/02/27 J Agric Food Chem. 2007 Mar 21; 55(6):2282-7. doi: 10.1021/jf063337e. Epub 2007 Feb 24" |
