David F. Marten

A New General Synthesis of Isoprenoid Chains Employing the Reaction of Dialkylcuprates with β-Acetoxy α,β-Unsaturated Esters

Abstract We recently reported the reaction of lithium dialkycuprates with β-acetoxy α,β-unsaturated esters which provides a stereoselective synthesis of the corresponding alkyl substituted α,β-unsaturated esters. We now report the application of this new reaction in a stepwise general synthesis of isoprenoid chains. The four carbon chain of the isoprene unit is derived from methyl acetoacetate while the isoprene side chain is introduced via lithium dialkylcuprates. Reaction of an alkyl halide with the dianion of methyl acetoacetate gives the γ-alkylated β-keto ester and accomplishes a four carbon chain extension of the alkyl halide.2,3 The β-keto ester can then be converted stereoselectively to the Z-isomer of the β-acetoxy α,β-unsaturated ester by reaction with isopropenyl acetate.4 Reaction of the β-acetoxy α,β-unsaturated ester with a lithium dialkylcuprate stereo-selectively replaces the acetoxy group with an alkyl group and accomplishes the introduction of the side chain of the isoprene unit. The res...

Competitive pathways in the reaction of acetylenic alcohols with the η5-cyclopentadienyl(dicarbonyl)(η2-2-methylpropene)iron(II) cation

The reaction of the title iron complex with but-3-yn-1-ol yields a 1 : 1 mixture of the η2-2,3-dihydrofuran complex (2) and the 2-oxacyclopentylidene carbene complex (3) while pent-4-yn-1-ol yields the η2-2-methylenetetrahydrofuran complex (6); η2-acetylene and vinylidene carbene complexes are proposed as intermediates.

Preparation and molecular structure of (3-acetyl-4,5-dihydrofuran-2-yl)tetracarbonylmanganese(I)

Treatment of cis-(2-oxacyclopentylidene)nonacarbonyldimanganese with butyl-lithium followed by acetyl chloride gives (3-acetyl-4,5-dihydrofuran-2-yl)-tetracarbonylmanganese whose molecular structure was determined by X-ray crystallography.