Reactions of Dimethoxycarbene with Dimethyl 2,3-Dicycanomaleate and Fumarate

Abstract

Dimethoxycarbene, in 2-fold or larger excess, reacts with dimethyl 2,3-dicyanomaleate and fumarate to afford an unstable dihydrofuran 1:1 adduct that was shown to react further with the carbene to afford a 2:1 adduct reported previously. In an astonishing process, the dihydrofuran reacts with water to afford a mixture of (d,l and meso) dimethyl 2,3-dicyanosuccinates in which both hydrogen atoms of water were used to hydrogenate a C=C bond.

Dialkyl dicyanofumarates and dicyanomaleates as versatile building blocks for synthetic organic chemistry and mechanistic studies

“…Dimethoxycarbene ( 6 ), generated in situ by thermal decomposition of 2,2-dimethoxy-2,5-dihydro-1,3,4-oxadiazole 7 , reacts with E - 1b yielding a mixture of the trans -configured tetramethoxycyclobutane 8 and 2,3-dihydrofuran 9 [ 21 – 22 ] ( Scheme 3 ). The latter reacts further with dimethoxycarbene and converts into the orthoester 10 via insertion into the C–O bond.…”

Carbenes and Nitrenes

“…Reaction of an excess of DMC with dimethyl 2,3-dicyanomaleate at 50 • C afforded a mixture of cyclobutane (63) and dihydrofuran (64). 101 Addition of tetramethoxyethene to maleate gave (64), whereas (63) was formed by addition of a second equivalent of DMC to an extremely reactive dihydrofuran intermediate (65) 1,3-Dibenzyl-2-cyanomethyl−2H -benzimidazoline was shown to undergo αelimination, generating an NHC that reacted as a nucleophile with a range of organic electrophiles. 102 Following an extensive use as metal ligands, NHCs are now finding new applications in the field of organocatalysis, as largely exemplified by the reviews cited previously.…”