Radical cyclization of 1,6-dienes with azobis(alkylcarbonitriles) on water under additive-free conditions

Abstract

Without using any additives, a practical and eco-friendly methodology has been realized for the tandem double cyclization of 1,6-dienes with easily accessible azobis(alkylcarbonitriles) on water.

Radical Cyclization of 1,n‐Enynes and 1,n‐Dienes for the Synthesis of 2‐Pyrrolidone

“…Based on our previous contributions to the use of 1, n ‐enynes as substrates in the preparation of 2‐pyrrolidones, we developed a green and practical bicyclic reaction method for the synthesis of 2‐pyrrolidone using 1,6‐dienes and easily available, substituted AIBN derivatives as starting materials and water as the solvent in 2020 (Scheme 28). [41] This new method demonstrated excellent functional group tolerance on the N ‐aromatic ring. For example, when the substituents on the N ‐aromatic ring of 1,6‐dienes were OMe, Me, Cl, and CN, the yields of the corresponding products were greater than 70%.…”

Nonconventional driving force for selective oxidative C–C coupling reaction due to concurrent and curious formation of Ag0

“…Formation of para-meta coupled product happens in presence of h exa f louro i so p ropanol (HFIP) solvent, where hydrogen bonding (around phenolic hydroxide) helps in increasing nucleophilic character at the ortho -position of methoxy group 4 , 13 . We want to point out here that, when the reaction of 2-naphthol was carried out in the presence of equimolar 2,6-di-tert-butyl-4-methyl phenol, it showed retention of large amount of unreacted reactant, indicating radical quenching of intermediate state 14 , 15 . This is in accordance with the formation of only para-para product (5aa), a radical–radical coupling pathway, as reported in literature.…”

One-pot, three-component Fischer indolisation–N-alkylation for rapid synthesis of 1,2,3-trisubstituted indoles

“…[13][14][15][16][17] Our recent studies into structurally-diverse spiropyrans 4,18 required a broad range of 1,2,3-trisubstituted indole building blocks and, to meet this demand, we have developed a rapid, cheap and concise one-pot, three-component sequence for their synthesis, based upon Fischer indolisation-N-alkylation, and the evolution of this process is described herein. 19 One-pot, multistep regimens can provide efficiency in terms of time, cost, yield, labour, energy and consumables, [20][21][22] and the combination of Fischer indole synthesis and indole N-alkylation is inherently geared towards successful application as a rapid one-pot process for two principal reasons: (i) Fischer indolisation and indole N-alkylation are robust, clean, high-yielding processes which generate minimal quantities of by-products or leftovers, hence are ideal within one-pot, multicomponent reaction cascades; (ii) indole N-alkylation is rapid (commonly < 1 hour) and whilst Fischer indolisation displays more varied reaction rate, use of microwave irradiation often leads to short reaction times (<10 minutes). 23 A further benefit to this Fischer indolisation-N-alkylation approach is that a broad range of structurallydiverse starting materials are commercially available for each of the aryl hydrazine, ketone and alkyl halide components, hence the process is amenable to rapid generation of trisubstituted indole libraries.…”