N-Acyl- and N-Sulfonylformamidines from Cyanamides and Carbodiimides by Hydroalumination and Subsequent Treatment with Electrophiles

Hydroalumination of cyanamides 1 with di(isobutyl)aluminium hydride affords intermediate compounds 3, which have dimeric structures in the solid state with four-membered Al2N2 heterocycles and exocyclic N=C double bonds. The reactions of 3 with acyl chlorides yield N',N'-disubstituted N-acylformamidines 5, whereas reaction with sulfonyl chlorides give the corresponding N-sulfonylformamidines 7. In contrast, carbodiimides 8 react with dialkylaluminium hydrides R2AlH (R = tBu, iBu) to give compounds 9 in which one C=N bond of the carbodiimide is reduced to form an amidinate ligand and a second molecule of the hydride is coordinated through an Al-N and an Al-H-Al bond. Treatment of 9 with acyl chlorides yields N,N'-disubstituted N-acylformamidines 10, whereas reaction with sulfonyl chlorides gives the corresponding N-sulfonylformamidines 11.