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

Abstract

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.

Chemoselective Hydroalumination of 1-Aza-but-1-en-3-ynes (C-Iminoalkynes): Formation of Propargylamines by Imine Reduction and of 5-Aluminazoles and 1-Aza-butadienes by Anti-Michael Attack

“…Then, diethyl ether was used as eluent to separate the reaction products from inorganic aluminum species. After removal of diethyl ether purification of the products was achieved by chromatography over nondried silica gel using cyclohexane/ethyl acetate-mixtures as eluent. Propargylamines 4a – e were obtained in 45–84% yield (Scheme , Table ) and were characterized by NMR spectroscopy (typical sp-carbon signals in 13 C NMR were at 90–100 ppm) and mass spectrometry.…”

Mild Reductive Functionalization of Amides into N‐Sulfonylformamidines

“…(Scheme 1 b and c) . The direct condensation of sulfonamides with N , N ‐dimethylformamide dimethyl acetal (DMF‐DMA) was furthermore reported by Sharma and co‐workers, and N ‐sulfonylformamidines can also be prepared from cyanamides …”

“…[13,14] The direct condensation of sulfonamides with N,N-dimethylformamide dimethyl acetal (DMF-DMA) was furthermore reported by Sharma and co-workers, [15] and N-sulfonylformamidines can also be prepared from cyanamides. [16] The development of the chemoselectiver eduction of amides has been very successful and, today,f unctional groups such as ketones, aldehydes,a nd imines can be tolerated. [17] Consequently,t he reductivef unctionalization of amides is now an emerging fieldw ithin organic chemistry.…”

Calcium formamidinate derivatives by hydride insertion of carbodiimides

“…In cases where the parent formamidinate species are required, analogous access necessitates the availability of a suitably reactive, molecular metal hydride. Documented examples of this latter process include rare earth metal (Y, [3][4][5] La 6 and Lu 7 ), transition metal (Fe, 8 Zr, 9 Nb, Ta 10 and Re 11 ), p-block (B, [12][13][14][15] Al, 16,17 Zn, [18][19][20] Ga 16 and Sn 21 ) and s-block metal (Li 22 and Mg 23,24 ) hydrides (Scheme 1(b)).…”