Ruthenium-Catalyzed Regioselective 1,3-Methylene Transfer by Cleavage of Two Adjacent σ-Carbon−Carbon Bonds:  An Easy and Selective Synthesis of Highly Subsituted Benzenes

Abstract

We report a new ruthenium-catalyzed 6-endo-dig cyclization of 6,6-cycloalkylidenyl-3,5-dien-1-ynes, which produces highly substituted benzenes with considerable structural reorganization. In this process, we observe a regioselective 1,3-methylene migration via extrusion from a cycloalkylidenyl ring, in addition to a regiocontrolled 1,2-alkyl migration. This cyclization provides an easy and convenient synthesis of complex benzenes bearing various different substituents.

Pericyclic Reactions Involving Catalytic Metal–Vinylidene Complexes

“…Iwasawa and co-workers have reported a method for the preparation of polyaromatic compounds by a tungsten-catalyzed 6 e À p electrocyclization of vinylidenes generated from aromatic enynes through an analogous mechanism to the previously described (Scheme 4). [9] The novelty in the Lius results is the regioselective 1,2-alkyl shift after the electrocyclization reaction of cyclopropylidenyl and cyclobutylidenyl derivatives 7 and 8 in presence of a 10 % of [Ru(Tp)- Scheme 6. Thus, o-(iodoethynyl)styrenes 5, in the presence of different amounts of W(CO) 5 in THF, generate iodinated tungsten-vinylidenes, which after 6 e À p electrocyclization give rise to iodo-substituted naphthalene derivatives 6 (Scheme 5).…”

Cycloisomerization of 1,n‐Enynes: Challenging Metal‐Catalyzed Rearrangements and Mechanistic Insights

“…(47)]. [65] The formation of the cyclopentene ring probably implies a 1,5-sigmatropic hydrogen shift of vinylideneruthenium intermediates. Such intermediates are also involved in the synthesis of functionalized aromatic rings.…”

Metal Vinylidenes as Catalytic Species in Organic Reactions

“…In the former case, a highly substituted benzene is formed (211, equation 1), [88] whereas in the latter case a 1,3-diene product is formed (213, equation 2). [89] The formation of product 211 can be explained by the proposed mechanism in Scheme 74.…”