Gold-catalysed regioselective cascade cycloisomerisation reactions of aza-enediynes for the synthesis of substituted benzoisoquinoline derivatives.

Aza-enediynes underwent a facile, regioselective gold-catalysed cascade cycloisomerisation to furnish dihydrobenzo[f]isoquinoline derivatives in excellent yields. The aza-enediynes were conveniently prepared via a formal vinylic displacement reaction of allyl bromosulfones. The latter functioned as a stable and easily accessible synthetic equivalent of allenyl sulfone.

The facile synthesis of 1-benzoazepine derivatives via gold-catalyzed regioselective cycloisomerization reactions of N-(o-alkynylaryl)-N-vinyl sulfonamides.

Gold-catalyzed, regioselective cycloisomerization of N-(o-alkynylaryl)-N-vinyl sulfonamides afforded high yields of 2-sulfonylmethyl-1-benzoazepine derivatives. This 7-endo-dig selective cyclization proceeds via the incorporation of an exocyclic double bond by a labile 1-benzoazepine intermediate. The cyclization substrates were assembled in two steps from readily available materials using Sonogashira coupling and a Cs2CO3-mediated formal vinylic substitution.

Catalyst-controlled divergence in cycloisomerisation reactions of N-propargyl-N-vinyl sulfonamides: gold-catalysed synthesis of 2-sulfonylmethyl pyrroles and dihydropyridines.

Gold-catalysed, divergent synthesis of 2-sulfonylmethyl pyrroles and dihydropyridines from N-propargyl-N-vinyl sulfonamides has been achieved. Echavarren's gold(I) catalyst promoted the formation of pyrrole derivatives whereas the combination of PPh3AuCl and AgSbF6 afforded dihydropyridines. The aza-enyne precursors for the cycloisomerisation reaction were prepared by a base-mediated formal vinylic substitution reaction of 2-bromoallyl sulfones.

Regioselective synthesis of substituted arenes via aerobic oxidative [3 + 3] benzannulation reactions of α,β-unsaturated aldehydes and ketones.

Facile conversion of α,β-unsaturated aldehydes and ketones into highly substituted arenes via a base-mediated, completely regioselective, air-oxidative [3 + 3] benzannulation reaction with readily available 4-sulfonylcrotonates or 1,3-bisphenylsulfonylpropene is reported. The reaction can also be carried out as a one-pot, three-component operation using 4-bromocrotonates, aryl sulfinates, and cinnamaldehyde. This open-flask, metal-free reaction does not require anhydrous solvents, proceeds under mild conditions, and uses atmospheric oxygen as the oxidant to afford high yields of the 3-(arylsulfonyl)benzoic acid esters.