boron trifluoride diethyl etherate in diethyl ether under Ar; Sn compd. treated with BF3*OEt2 in ether; hydrolyzed with NaHCO3; detd. by (1H) NMR spectra; E and Z isomers of aldehyde (84:16) and small amt. of Z isomer of the initial Sn compd. obtained;

boron trifluoride diethyl etherate; copper (I) cyanide in diethyl ether under Ar; Mg compd. reacted with CuCN in ether (2:2, -45°C, 30-40min); BF3*OEt2 and Sn compd. reacted in ether (1:3, -80°C, 10 mi n or -45°C, 40 min); soln. of Sn compd. cannulated on soln. of Mg-Cu compd. (-80 or -40°C, 1 h); hydrolyzed with NaHCO3; chromd. (silica gel, MeCN-CH2Cl2 80:20); detd. by (1H) NMR spectra;