n-butyllithium; ammonium chloride in tetrahydrofuran; hexane

in tetrahydrofuran 1 h;

in tetrachloromethane 1.5 h; Irradiation; Yield given;

in chloroform-d1; methanol-d4 2 h; Irradiationphotochemical dimerization, further reaction in dependence of solvent (CCl4, CD3CN, CDCl3) and in presence of NaN3 as inhibitor; Mechanism;