Intramolecular Substitution Reaction of Lithium Alkylidene Carbenoids. Regioselective Synthesis of Indenes

Abstract

When 4,4-dibromo-3-alkenols are treated with butyllithium, an intramolecular substitution reaction with alkoxide moiety occurs at the lithium alkylidene carbenoid center to give dihydrofurans. The reaction mechanism of this intramolecular substitution reaction is studied by B3LYP density functional calculations with the 6-31+G(d) basis set, and the substitution is found to proceed in a concerted manner. This substitution reaction is applied to the regioselective preparation of indene derivatives. That is, treatment of 3-(o-bromophenyl)-1,1-dibromopropene derivatives 23 with butyllithium results in the formation of intramolecular substitution intermediates, 3-indenyllithiums D, which are trapped with electrophiles to afford substituted indenes regioselectively.

A New Method for the Preparation of Non‐Terminal Alkynes: Application to the Total Syntheses of Tulearin A and C

“…However, the observation that sBuLi and even tBuLi are particularly effective reagents makes this scenario highly unlikely, because the efficient alkylation of a lithium acetylide by sBuCl or tBuCl is improbable, if not impossible. [25] Rather, metal vinylidenes of type 6 are known to be amphiphilic; it is their electrophilic rendition that is believed to be the key enabling feature, [26][27][28] in that it allows such species to intercept a second equivalent of RLi to give 8 prior to reductive elimination (path B). [29] Under this premise, it is plausible that the initial Li/Cl exchange is rate-determining; otherwise, it would be difficult to explain why tBuLi reacts much faster than MeLi (cf.…”

Theoretical and Experimental Study on the In-Plane SN2-Type Substitution Reaction of Haloalkenes with Inversion of Configuration at the sp2 Carbon

“…During the course of our study on the nucleophilic cyclization of haloalkenes, , one of us found that the cyclization of fluoroalkene E -1a occurs via the in-plane S N 2 pathway in an Onsager continuum model for dimethylformamide (DMF) (Δ G = 25.8 kcal/mol) and occurs via a concerted π-addition−elimination pathway in the gas phase [B3LYP/6-31+G(d)] (Scheme ) . This mechanistic change inspired us to do further study on the in-plane S N 2 reaction.…”

Nickel-Catalyzed Vinylidene Insertions into O–H Bonds

“…There are many examples of catalytic carbene insertions into O–H bonds using diazoalkanes . However, insertions of vinylidenes into O–H bonds are more limited in scope, despite their potential value in the preparation of unsaturated oxolanes such as 2,3-dihydrofurans and furans.…”