Gold(i) catalysed sequential dehydrative cyclisation/intermolecular [4 + 2] cycloaddition of alkynyldienols onto activated alkynes/alkenes: a facile route to substituted norbornadienes/norbornenes

Abstract

One-pot synthesis of highly substituted norbornadienes/norbornenes via gold-catalysed dehydrative cyclisation of alkynyldienols, followed by intermolecular [4 + 2] cycloaddition of in situ generated cyclopentadiene and activated alkynes/alkenes is described. The precursors, alkynyldienols, are obtained via sequential Sonogashira cross-coupling of 3-bromoenals, alkyne addition and reduction. Yields of the enynals and multisubstituted norbornadienes in all the cases are good to excellent.

Exploring the gold mine: [Au]-catalysed transformations of enynals, enynones and enynols

“…Our research group has developed a new route for the synthesis of norbornadiene derivatives 205 via dehydrative cyclisation followed by intermolecular [4 + 2] cycloaddition of alkynyldienols 202 with activated alkynes 203 under mild conditions (Scheme 63). 74 This methodology was extended to activated alkenes 204 and led to norbornenes 206. The alkynyldienol precursors were synthesised by the reduction of the corresponding alkynyldienals; these dienals were prepared by Sonogashira cross coupling followed by alkyne addition between 3-bromoenals and terminal alkynes.…”

Synthesis of functionalized unsymmetrical 1,3-butadiene-3-yne derivatives from β-halo styrene derivatives and their application in the synthesis of trisubstituted pyridines

“…While our work is under progress, Swamy and coworkers reported the synthesis of norbornadienes/norbornenes starting from alkynyldienols in the presence of Au catalyst. 10 The starting material alkynyldienol is obtained from Sonogashira crosscoupling of 3-bromoenals to terminal alkynes followed by alkyne addition and reduction. Although they prepared dienynal derivative, further studies are not carried out on the role of the functional group during the alkyne addition step to enynal derivative.…”