Russian Journal of Organic Chemistry, Vol. 41, No. 11, 2005, pp. 1601-1609. Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 11, 2005, pp. 1635-1643. Original Russian Text Copyright Ó 2005 by Sheshenev, Baird, Bolesov. 1070-4280/05/4111-1601Ó2005 Pleiades Publishing, Inc. Synthesis of 1-Bromosubstituted Analogs of cis-Deltamethrinic and cis-Permethrinic Acids A.E. Sheshenev 1 , M.S. Baird 2 , and I.G. Bolesov 1 1 Moscow State University, Moscow, 119992 Russia e-mail: ivbolesov@mail.ru 2 Department of Chemistry, University of Wales, Bangor, Gwynedd, LL57 2UW, UK Received June 25, 2005 AbstractIn the synthesis of 1-bromosubstituted analogs of cis-deltamethrinic and cis-permethrinic acids, main components of pyrethroids, the key stage is an intramolecular 1,4-O,C-acyl transfer in reactions of 1-acyloxymethyl- 2,2-dibromocyclopropanes with methyllithium. An important groups among synthetic pyrethroids consists of the derivatives of gem-dimethylcyclopropane where the unsaturated and ester functions of the molecule are present in the cis-orientation [1]. For instance, the cipermethrin (I, R = Cl) and deltamethrin (I, R = Br) (Scheme 1) are regarded as most efficient insecticides possessing high activity, photostability, and relatively low toxicity with respect to mammals. Among the versatile stereoselective syntheses of these compounds the following methods may be listed: asym- metrical enantioselective cyclopropanation of 4,4-dihalo- 2-methylbuta-1,3-dienes [2], using chiral substrates in intramolecular cyclopropanation [3] or in reactions with sulfur or phosphoruc ylides [4], Faworsky rearrangement with individual enantiomers of 2-chlorocyclobutanones [5], application of chiral lactams [6], enzymatic desymmetriza- tion of 1,4-cyclohexanedione derivatives [7], and also employing natural compounds, e.g., (+)-3-carene [8]. The other general procedures of pyrethroids syntheses [1, 9] involve diazopropane addition to alkynes [10], Claisen re- arrangement [11], Grob fragmentation [12], and Grignard reagents addition to 3,3-dimethylcyclopropenes [13]. The goal of this study was synthesis of bromosub- stituted pyrethroids based on selective transformations of 1-acyloxymethyl-2,2-dibromo-3,3-dimethylcycloprop- anes under the action of methyllithium. The reaction of esters of 2,2-dibromocyclopropylmethanols with methyl- lithium is known to result in a cis-1,4-O,C-migration of the acyl group initiated by the replacement of the cis-bromine by lithium (Scheme 2, transitions II > III > IV) [14]. The given scheme proved to be sufficiently effective in transition to 1-bromo-cis-hydroxymethyl ketones (V, R' = H, CH 3 ). In this connection the extension of that re- arrangement to the corresponding 1-acyloxymethyl deriv- atives of 2,2-dibromo-3,3-dimethylcyclopropane deserved attention. The choice of acyl groups to be transferred from the oxygen to the carbon atom in the small ring allowed for their transformation into substituents at the small ring traditional for pyrethroids (or their analogs). Scheme 1. Scheme 2. &2 5 5 & + 23KP &1 , + 5&O%U Dedicated to Academician of the Russian Academy of Sciences N.S.Zefirov on occasion of his70 th anniversary