Catalytic Asymmetric Diazoacetate Cyclopropanation of 1-Tosyl-3-vinylindoles. A Route to Conformationally Restricted Homotryptamines.

Substituted 1-tosyl-3-vinylindoles undergo catalytic asymmetric cyclopropanation with ethyl- and tert-butyldiazoacetate to afford N-protected trans-2-(indol-3-yl)-1-cyclopropanecarboxylic esters in good yield and high enantiomeric excess (81−88% ee). The resulting cycloadducts are demonstrated to be useful intermediates for the synthesis of conformationally restricted, homotryptamine-like analogues such as BMS-505130.