Direct incorporation of A 6α(7α)-formamido group into penicillins and cephalosporins

6β(7β)-($\text{N}$-2,2,2-Trichloroethoxycarbonyl-$\text{N}$-trifluoromethanesulphonylamino) penicillins and cephalosporins have been converted into the corresponding 6α(7α)-formamido-6β(7β)-2,2,2-trichloroethoxycarbonylamino derivatives, by treatment with $\text{N}$,$\text{N}$-bis(trimethylsilyl) formamide and triethylamine.