Regioselective differentiation of vicinal methylene C–H bonds enabled by silver-catalysed nitrene transfer
作者:Ryan J. Scamp、Bradley Scheffer、Jennifer M. Schomaker
DOI:10.1039/c9cc04006d
日期:——
Silver-catalyzed nitreneinsertion enables the formation of benzosultams in good yield and with regioselectivity complementary to other transition metal nitrene-transfer catalysts. Preferential formation of six-membered benzosultam rings predominates for alkyl-substituted benzenesulphonamide precursors. Ligand-controlled tunability is also achieved for benzenesulphonamides with γ-branched alkyl substituents
A novel pathway for the preparation of 3, 4-dihydro-2H-1λ6-benzo[e][1, 2]thiazine 1, 1-dioxides 3 via an orthomethyl lithiation/cyclization reaction of N-acyl-o-toluenesulfonamides 5 is reported. Readily available N-acyl-o-toluenesulfonamides 5 were treated with 2 eq of n-BuLi at -78°C-0°C to give the corresponding sultams 6 in moderate to good yields. The resulting sultams 6 were converted to saturated sultams 3, which can be considered as one carbon-extended homologues of the Oppolzer sultams 1, in high yields by hydrogenation. Studies on the scope and limitation of this annulation for the preparation of sultams are discussed. Demonstration of the feasibility of using the sultams 3 templates for an electorophilic fluorinating agent is also described.