in tetrahydrofuran T=-70°C; 0.666667 h; Yield given. Yields of byproduct given. Title compound not separated from byproducts;

trifluoroacetic acid in tetrahydrofuran T=-70°C; influence of the nature of protonating agent; Product distribution;

in tetrahydrofuran T=-70°C; 0.0833333 h; further solvent; Further byproducts given. Yields of byproduct given. Title compound not separated from byproducts;