Reactions of Vinylphosphonates. 2. Synthesis of Functionalized Dienes, Trienes, and Their Analogues. Synthetic Aplications to Regioselectively Functionalized Benzene Derivatives

Article abstract of DOI:10.1021/jo00133a025

The phosphoryl-stabilized carboanions prepared from vinylphosphonates 1a,b and various carbanions 2a-c react with aldehydes 3 to give olefins having various functional groups.The dienes 5c-g produced by the reaction using α,β-unsaturated aldehydes and a methyl (methylsulfinyl)methyl sulfide carbanion (2b) easily undergo thermolysis to afford reactive intermediate 1-methylthio 1,3,5-trienes, which are converted into the 1,4-disubstituted benzenes 7a-e in 27-56percent overall isolated yields via the electrocyclic reaction into cyclohexadienes and subsequent elimination of methanethiol.Thermolysis of the reaction product using ethyl α-(diethylphosphono)acrylate (1a), 2b, and 1,4-bis(2-formylethenyl)benzene (3g) produces 4,4''-bis(ethoxycarbonyl)-1,1':4',1''-terphenyl (7f) in 16percent yield.The reaction using an ethyl (methylthio)acetate carbanion (2c) instead of 2b gives thermally stable dienes 5i-l in 38-52percent yields.Oxidation of the dienes 5i,k,l followed by thermolysis, leads to the 1,2,4-trisubstituted (8a,b) and 1,2-disubstituted benzenes (9).Similar treatment of the product 5m derived from 1a, 2c, and 3-phenylpropargylaldehyde (3f) produces a mixture of 2,4-bis(ethoxycarbonyl)biphenyl (8a) and ethyl 4-(ethoxycarbonyl)-7-phenylhepta-2,4-dien-6-ynoate (11) in 23percent and 32percent yields.