Iminodiaziridines by Regio- and Stereoselective Cyclization of Diastereomeric Singlet Triazatrimethylenemethane Diradicals Generated Through Photolysis of 5-Imino-4,5-dihydro-1<i>H</i>-tetrazoles
                                
                                    
                                        作者:Helmut Quast、Lothar W. Bieber                                    
                                    
                                        DOI:10.1021/jo702697f
                                    
                                    
                                        日期:2008.5.1
                                    
                                    1,4-Dialkyl-5-(N-alkylimino)-4,5-dihydro-1H-tetrazoles were prepared in high yields by deprotonation with sodium hydride of 1,4-dialkyl-5-(N-alkylamino)tetrazolium salts that were adorned with two or three different alkyl groups, including methyl, trideuteriomethyl, and tert-butyl groups. Direct irradiation (lambda > 255 nm) at -60 degrees C yielded molecular nitrogen and mixtures of 1,2-dialkyl-3-(N-alkylimino)diaziridines (83-87%) along with carbodiimides (13-17%) arising by 1,3-dipolar cycloreversion. The missing 1,3-dipoles, alkyl azides, did not survive photolysis. Each member of a pair of isotopomers and of a pair of isomers, and an iminodihydrotetrazole, whose three nitrogens were tagged, yielded a characteristic mixture of three isomeric iminodiaziridines that allowed the mode of formation to be deduced. The results are interpreted in terms of photodenitrogenation of the iminodihydrotetrazoles to furnish diastereomeric singlet triazatrimethylenemethane diradicals that retain the inherited configurations before ring closure to iminodiaziridines, presumably in two steps via mono-orthogonal diradicals.