The reaction of phosphines and amides with diethyl azodicarboxylate (DAD) produced phospha-λ5-azenes. Thus aromatic amides and those aliphatic amides with electron-withdrawing substituents gave N-acyl-P,P,P-triphenylphospha-λ5-azenes (5) when triphenylphosphine (TPP) was employed. Both aryl-and alkylsulfonamides reacted with TPP and DAD to produce the N-sulfonylphospha-λ5-azenes (9). Diphenylphosphinamide (10) and ethyl carbamate (12) also produced the respective phosphazenes (11 and 13) with TPP and DAD. Secondary carboxamides and sulfonamides did not react with TPP and DAD. The reaction of triethyl phosphite with sulfonamides in the presence of DAD produced the phosphorimidates (20) in an analogous reaction, along with the corresponding N,N-diethylsulfonamides and the deethylated adduct of triethyl phosphite and DAD (23). Triethyl phosphite-DAD failed, however, to give a phosphorimidate with carboxamides but gave, instead, the rearranged adduct of DAD and triethyl phosphite (19). Tris(dimethylamino)phosphine reacted with sulfonamides and DAD but the products were the corresponding ethyl N-sulfonylcarbamates (26) rather than the phosphazenes. Tris(dimethylamino)phosphine reacted with azodicarbonamide (a molecule which contains both the azo and carboxamide groups) with the production of N,N-dimethylurea, again without formation of the phosphazene. Finally, the reaction of triphenylarsine with benzenesulfonamide and DAD produced N-(phenylsulfonyl)tri-phenylarsa-λ5-azene (30) but triphenylstibene with DAD and benzenesulfonamide only gave triphenylstibene oxide. Mechanistic possibilities for these reactions are also discussed.
ASJC Scopus subject areas
- Organic Chemistry