ARS | Publication request: Two-carbon homologation of aldehydes and ketones to a,ß-unsaturated aldehydes

Submitted to: Molecules
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 13, 2011
Publication Date: June 17, 2011
Citation: Petroski, R.J., Vermillion, K., Cosse, A.A. 2011. Two-carbon homologation of aldehydes and ketones to a,ß-unsaturated aldehydes. Molecules. 16(6):5062-5078.

Interpretive Summary: The study of insect chemical ecology requires the synthetic preparation of insect pheromones, some having complex molecular structures. This paper describes a novel preparation of difficult to obtain synthetic intermediates, useful for the total synthesis of certain complex target compounds. The research was conducted to enable access to suspected pheromones potentially useful for the biological control of the emerald ash borer and other high-priority research objectives. These results are important to scientists in industry because synthetic pathways must be economical and capable of scale-up in order to be commercially viable.

Technical Abstract: Phosphonate reagents were developed for the two-carbon homologation of aldehydes or ketones to unbranched- or methyl-branched a,ß-unsaturated aldehydes. The phosphonate reagents, diethyl methylformyl-2-phosphonate dimethylhydrazone and diethyl ethylformyl-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 1 M HCL and petroleum ether. This robust two-step process worked with a variety of aldehydes and ketones. Overall isolated yields of unsaturated aldehyde products ranged from 71% to 86% after the condensation and deprotection steps.