Computational Investigation of the Reactivity of a Hexadienyne Derivative

Abstract

[reaction: see text] The mechanisms of perphenylbutenyne reactivity are examined through B3LYP and multireference ab initio calculations on model systems. Calculations for the formation of a naphthalene derivative suggest a process similar to that seen previously in the literature. A new mechanism for perphenylbutenyne dimerization to form a semibullvalene derivative is proposed and supported by calculations.

Ene‐ene‐yne Reactions: Activation Strain Analysis and the Role of Aromaticity

“…It is widely accepted that this transformation involves the initial formation of the key bent‐allene 2 intermediate (also known as isobenzene) from which successive 1,2‐hydrogen migrations occur to form the aromatic ring 2. 6 The first step of this mechanism, the so‐called Hopf cyclization, is thought to be similar to the Bergman cyclization of cis ‐3‐hexene‐1,5‐diynes,7 which is suggested to proceed through an in‐plane aromatic transition state 8. The resemblances of both processes are evident as the corresponding six‐membered ring closures occur at temperatures around 200–250 °C with quite similar activation barriers of around 30 kcal mol −1 9…”

Reaction mechanisms : Part (ii) Pericyclic reactions

“…52 7 Tandem and hybrid reactions Tandem reactions A new mechanism for the formation of semibullvalene derivatives from dienynes (Scheme 31) was suggested by Litovitz, Carpenter and Hopf based on computational studies (using B3LYP and multireference ab initio methods). 53 This mechanism (shown below for a model of the more heavily substituted system studied experimentally) involves a series of pericyclic reactions of the electrocyclization, cycloaddition (both concerted and stepwise) and sigmatropic types. The authors note that the semibullvalene product does not undergo Cope rearrangement, since, in this case, such a reaction would disrupt the aromaticity of the appended ring.…”

Hydroalumination-Triggered Cyclization of Silylated 1,3-Dien-5-ynes to Polysubstituted Benzenes

“…In the absence of DIBAL-H, dienyne 1a was recovered intact (entry 6). This control experiment makes it clear that the present reaction is not just a thermal electrocyclization of 1,3-dien-5-ynes . A reduced amount of DIBAL-H (0.2 equiv) hardly promoted the cyclization (entry 7).…”