boron trifluoride diethyl etherate 1) CHCl3, r.t., 30 min, 2) CDCl3, 60 deg C, 28 h; Yield given. Multistep reaction. Yields of byproduct given;

BF3-Et2O in chloroform the triacetate and the enol ether are dissolved in dry CHCl3, BF3-Et2O is added, the mixt. is stirred at room temp. for 30 min; the volatile components are evaporated at 25°C and 1 mmHg;

sodium azide in dimethyl sulfoxide 2.5 h; Ambient temperature;

in dimethyl sulfoxide a mixt. of NaN3 and aryllead triacetate in dry DMSO is stirred for 2.5 h in the dark at room temp.; the residual after work-up is filtered, with protection from light, through a column of silica gel, elution with with light petroleum;