Dimethyl hexenedioates, preparation

Ruthenium-catalyzed hydrodimerization of acrylonitrile under hydrogen atmosphere to give adiponitrile (393) is a useful coupling reaction [154], Dimethyl hexenedioates (394a and 394b) are formed by dimerization of methyl acrylate by Pd, Ru and Rh catalysts. In particular the catalyst prepared by the treatment of RuC12 with Zn and... 

RhCp (C2H4)(CH2CH2- -H)] which is prepared by protonation of RhCp (C2H4)2, is a highly active catalyst for tail-to-tail dimerization of methyl acrylate to dimethyl hexenedioates (eq (51)) [61]. 

Dimethyl-3-hexenedioic acid (171) was also prepared by an intermolecular diacylation of the dibromide 170 with 2-lithio-l,3-dithiane (161), followed by deprotection and final oxidation (Scheme 48)214. 

Conjugate addUion-cyclization. 3-Substituied 2-carbomethoxycyclopentanones are prepared conveniently in one step from dimethyl (2E)-hexenedioate by conjugate addition of lithium dialkyl cuprates or higher-order cyan[Pg.348]

An improved method for the preparation of methyl 2-oxo-5-vinyl-cyclopen-tanecarboxylate (389) by treatment of dimethyl ( )-2-hexenedioate (390), with the cuprate made from vinyllithium and copper(I) cyanide (77-85%), led to a short synthesis of mitsugashiwalactone (391) (Scheme 34), another noriridoid isolated from Boschniaka rossica Borohydride reduction and dehydration gave methyl 5-vinyl-l-cyclopentenecarboxylate (392), and this could be cyclized by hydroboration and extended treatment with hydrogen peroxide—conditions for the highest yield in the cyclization seem to be with hydroboration in base— then a separate acid-catalyzed cyclization. The methyl group was added with lithium dimethyl cuprate. ... 

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