Dimethyl acetylendicarboxylate

Trimethylsilylmethylazide condenses easily with acetylenic dipolarophiles as dimethyl acetylendicarboxylate (DMAD) to give corresponding trimethylsilylmethyl-1H-1,2,3-triazoles.262... 

Dimethyl 1,4-cyclohexadiene-1,2-dicarboxylate has been traditionally prepared by three methods (i) dimethyl 3-vinyl-1,2-dichlorocyclobutane-1,2-dicarboxylate undergoes a ring expansion, with concomitant loss of the chlorine atoms to give the cyclohexadiene in 52% yield, upon treatment with Ni(CO)4 in refluxing benzene-dimethylformamide [68], (ii) butadiene sulfone and dimethyl acetylenedicarboxylate have been allowed to reflux in xylene for 150 min, and (iii) butadiene and dimethyl acetylendicarboxylate have been mixed in dioxane in a sealed tube, and allowed to stand at room temperature for 5 days [69]. 

Scheme 45 summarizes a novel method to prepare dimethyl l,4-cyclohexadiene-l,2-dicarboxylate. The method starts from 2 equiv of acetylene and 1 equiv of dimethyl acetylendicarboxylate, and uses the 0s(02CCH3)(P Pr3)2 unit as a template. This unit is introduced in the form of the dihydride-acetate complex 170 [66]. 

Saito, T., and T. Hiraoka Reactions of Iminophosphoranes of a-Amino Acid Derivatives with Dimethyl Acetylendicarboxylate. An Application to a Synthesis of 7a-Methoxycephalosporins. Chem. Pharm. Bull. 25, 1645 (1977). 

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