Waste-Free Chemistryof Diazonium Salts and Benign Separation of Coupling Products in Solid Salt Reactions

摘要

Gas-solid and solid-solid techniques allow for waste-free and quantitative synthesies in the chemistry of diazonium salts. Five tehcniques for diazotations with the feactive gases No_2, NO and NOCl are studied. Two types are mechanisteically investigated with atomic force microscopy (AFM) and are intrpreted on the basis of known crystal packings. The same principles apply to the cascade reactions that had been derived from one-step reactions. Solid diazonium salts couple quantitatively with solid diphenylamine and nilines to give the triazenes. Azo couplings are achieved with quantitiative yields by cautions co-grinding of solid diazonium salts with #beta#-naphthol and C-H acidic heterocycles, such as barbituric acids or pyrazolinones. Solid diazonium salts may be more easily applied in a stoichiometric ratio for couplings in solution. Co-grinding of solid diazonium salts with KI gives gunatitative yields of various solid aryl ioidides. The unavoidable coupling products in salt reactions are completely separated from the insoluble products in a highly benign manner. The solid-state reactions compare favourably with similar solution reactions that produce much waste. The structures of the products are elucidated with IR and NMR spectrosopy and mass spectrometry, while the tautomeric properties of the compounds are studied with density functional calculations at the B3LYP/6-31G~* and BLYP/6-31G~(**) levels.