Biaryle, Stilbene, Benzo[c]cinnoline und Dibenz[c,mn] acridine aus Sulfonamiden

Metal Free Bi(hetero)aryl Synthesis: A Benzyne Truce–Smiles Rearrangement

“…[7] Given that arynes undergo smooth addition to heteroatom nucleophiles, [8] we wondered if this feature could be exploited in am etal-free biaryl synthesis through addition/ rearrangement chemistry.O ur synthetic plan is set out in Scheme 1b.S tarting with readily available aryl sulfonamides (1), addition of abenzyne [generated from a2-trimethylsilyl-(phenyl) triflate precursor upon treatment with fluoride] should give the adduct 2.T his intermediate could then undergo aS miles-type ipso substitution with SO 2 extrusion, thus affording a2 -amino-biaryls 4,w hich are versatile molecules for further synthesis.Whilst Smiles rearrangements of stabilized carbanions are well known (the Tr uce variation), [9] ther earrangement of less-stable aryl anions as proposed here is very rare.Aseminal report from Pütter and Waldau described an aryl Tr uce-Smiles reaction for stabilized phenolate anions,a nd more recent work from Quayle and co-workers described aT ruce-Smiles rearrangement of a-silyl-phenylsulfonate esters. [10] Further encouragement for the idea came from the Motherwell biaryl synthesis, which demonstrates an analogous process under ar adical manifold. [11] Tr eatment of the haloaryl sulfonamides 5 with nBu 3 SnH affords 2-amino biaryls through radical ipso substitution and SO 2 extrusion (Scheme 1c).…”