Catalytic Cycloisomerization of Enyne Diesters Derived from Biaryls and Related Substrates

Abstract

Enyne diesters derived from biaryls and related substrates undergo intramolecular [2 + 2]cycloaddition and concomitant cyclo-reversion when treated with 10 mol% In(OTf) 3 in 1,2-dichloroethane. This enyne metathesis type cycloisomerization reaction enables the synthesis of phenanthrene, benzophenanthrene, benzotetraphene and other polycyclic (hetero)aromatic compounds bearing a synthetically useful diethyl β-(hetero)arylidene malonate moiety in a step-and atom-economic manner. In(OTf) 3 -catalyzed two independent intramolecular cycloisomerization on substrates 5 a and 5 b provides direct access to benzotetraphenes 6 a and 6 b containing bis(diethyl β-phenylmethylene malonate) moiety. Tetrasubstituted vinylidene malonate 4 a, substiututed by two different aromatic groups, is stereoselectively converted into Eand Z-isomer of triaryl group containing all carbon tetrasubstituted olefins (8 a, 8 a' and 8 b) via Pd-catalyzed stereoselective decarboxylative arylation reaction.

Highly Stereoselective Synthesis of Multisubstituted Olefins from Alkynyl Tetracoordinate Borons and Iodonium Ylides via a Cyclic Intermediate

“…Nevertheless, the highly regio- and stereoselective synthesis of multisubstituted olefins are always a significant challenge in organic synthesis. In spite of the considerable efforts that have been devoted to the development of efficient strategies for the construction of such olefin skeletons, many methods suffer from the disadvantage that the preference for the selective formation of E- or Z -isomers is highly substrate-dependent or transition-metal and expensive ligands are required (Scheme A) . In addition, alkyne migration reactions can also provide an alternative approach to multisubstituted olefins.…”