Carbodi-imines

The efficient conversion of the furazans (70) into 1,4-dinitriles (71) is thought to occur via the nitrile oxides (72). Thermal decomposition of the diaziridones (73) in the presence of triethyl phosphite gives the phosphine-imine (75) and the isocyanate (74), which subsequently react together to give the carbodi-imide (76). ... 

A very useful preparation of 1,3,5-thiadiazine type rings involves the report of Goerdeler and Ludke167 that 154 undergoes reaction with phenyl isocyanate to give 162 (X = Ph, Y = 0) and with carbodi-imides to give 162 (X = R, Y = NR ). Other compounds 163 may be prepared by treatment of 154 with benzaldehyde imines,167 a process which was also recently utilized by Kristian et al.3oa... 

Regiospecific, Pd(II) catalysed, cycloaddition reactions of azetidines to yield ring-enlarged products include the formation of tetrahydro-2-iminopyrimidines (e.g. 10) by reaction with carbodi-imides (95JOC253) and tetrahydro-l,3-thiazin-2-imines (e.g. 11) from isothiocyanates (95JOC3092). 

The thermolysis of 2-methyl-5-phenyl-l,3,4-oxadiazol-2-(3H)-one 106 produces a nitrile imine intermediate 105 which rearranges to the carbodiimide 107. The same carbodi-imide is obtained in the thermolysis of 2-methyl-5-phenyltetrazole 104. 

A number of unsaturated substances, such as ketone, azobenzene, imine, a-diimine, carbodi-imide, nitrile, CO2, and so on can be reduced by divalent samarium complexes. For example, reaction of bi(methylcyclopentadienyl) samarium complex with carbodiimide generates, via reducing-coupling reaction, the first structurally characterized bimetallic oxalamidino complex (Figure 8.34) [114]. 

Lactams can be prepared by [2 + 2] cycloadditions of mines and ketenes50- 52, iniines and ester enolatcs53, imines and silyl ketene acetals, alkenes and isocyanates54 56 and carbodi-imides and ketenes. The stereospecificity of these reactions has been extensively investigated due to the tremendous practical importance of 0-lactam antibiotics57 -59,1I3. 

Carbodi-imide-mediated reaction with carboxyhexyl-agarose Reaction with nylon imidate Adsorption onto nylon activated with triethyloxonium tetrafluoroborate glutaraldehyde cross-linking onto a nylon-polyethylene-imine copolymer Reaction with nylon imidate... 

Therefore, with respect to (x) orbitals (or ionizations of corresponding orbitals) allene (11), ketene imine (49), and ketene (43) represent no proper isoelectronic series (Section I1.G.3). And consequently, with respect to the preceding problems the correct application of the isoelectronic principle requires that concerning x ionizations ketene imines should be compared with carbodi-imides and isocyanates. 

A miscellany of papers dealing with the potency of the thioureido neighbouring group in nucleophilic substitution processes, the complexing ability of thioureas towards macrocyclic polyethers, and the cycloaddition reactions of thiocarbamoyl isothiocyanates (190) with ketens, ketenimines, imines, isocyanates, carbodi-imides, and isonitriles also deserve attention. 

When C=N groups are part of a heterocumulene system, as in ketenimines and carbodi-imides, they readily undergo [2+2] cycloaddition reactions with isocyanates. For example, C,C-diphenyl-A -p-tolylketenimine 138 reacts with phenyl isocyanate to give the four-membered ring cycloadduct 139 in 83 % yield. The cycloaddition proceeds exclusively across the C=C bond of the ketene imine. ... 

Another new -lactam synthesis proceeds via the hitherto unknown chloro-cyanoketene, obtained by thermolysis of various /8-azidoenones. Hence, when the crotonolactone (160) was refluxed in benzene in the presence of dicyclohexyl-carbodi-imide 88% of the adduct (161) was obtained similarly thermolysis of (160) with ethoxymethylene aniline gave 48% of (162). The reactions are stereospecific, and only one diastereoisomer was obtained. Thermolysis of 4-azidopyrrolin-3-one (163) in benzene gave 58% of the j8-lactam (165) directly, the zwitterion (164) being implicated without direct evidence such intermediates have already been proposed as precursors of jS-lactams when ketenes add to imines. The f -stereo-... 

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