Diazirines special

Whereas oxaziridine and diaziridine were partial subjects of comprehensive theoretical studies on cyclic compounds (73MI50800), diazirine and some of its simple derivatives were the special target of quantum chemical investigations. Since diazirine, the lowest molecular weight heterocycle, has only five atoms and is of high symmetry, there was a chance for ab initio calculations, which followed some semiempirical studies. 

With some special diazirines interconversion with diazoalkanes was observed on illumination (79AHC(24)63), e.g. with diazirinecarboxylic acid piperidide (194), spirodiazirine (195) and the tetracyclic ketodiazirine (196) (78CC442). 

The diazirines are of special interest because of their isomerism with the aliphatic diazo compounds. The diazirines show considerable differences in their properties from the aliphatic diazo compounds, except in their explosive nature. The compounds 3-methyl-3-ethyl-diazirine and 3,3-diethyldiazirine prepared by Paulsen detonated on shock and on heating. Small quantities of 3,3-pentamethylenediazirine (68) can be distilled at normal pressures (bp 109°C). On overheating, explosion followed. 3-n-Propyldiazirine exploded on attempts to distil it a little above room temperature. 3-Methyldiazirine is stable as a gas, but on attempting to condense ca. 100 mg for vapor pressure measurements, it detonated with complete destruction of the apparatus." Diazirine (67) decomposed at once when a sample which had been condensed in dry ice was taken out of the cold trap. Work with the lower molecular weight diazirines in condensed phases should therefore be avoided. 

The cyclic diazo compounds (diazirines 65) are very unreactive compounds. Specially noticeable is the absence of the reactivity toward electrophilic reagents which is characteristic of the linear isomers. Acids or aldehydes which react smoothly with the aliphatic diazo compounds are without action on the cyclic diazo compounds. Iodine does not attack the cyclic diazo compounds. 

In the last decade, experimental structural methods have been applied in specialized facets of diazirine chemistry, particularly with regard to supramolecular diazirine species and a detailed examination of diazirine decomposition. 

More attention has been paid to photoelimination of nitrogen from cyclic azoalkanes. Diazirine is a special case and undergoes decomposition via an identifiable carbene, with evidence in some cases for the intermediacy of a linear diazoalkane. The infrared spectra of phenylbromocarbene and phenyltrifluoromethy1-carbene, generated by photolysis of the corresponding diazirines... 

Two bonds formed by a N atom having one or two lone pairs would be expected to be angular with bond angles of 120 (one lone pair, sp bonds) or 109 (two lone pairs, sp bonds). (Molecules such as diazirine (cyclic diazomethane) and perfluorodiazirine are special cases like cyclopropane or ethylene oxide.) If the... 

Comparison of reactions of halocarbenes, which were produced from either alkylhalodiazirines by nitrogen extrusion, or by the usual method of eliminating hydrogen halide from dihaloalkanes by means of strong bases, bears special interest. Thus phenylchlorocarbene 177 was produced both from benzylidene chloride by potassium-t-butoxide, and by photolysis of phenylchlorodiazirine. ° Competition experiments with mixtures of olefins showed rate differences, especially remarkable for the isobutene-tetramethylethylene pair. The rate proportion was 0.20 when the diazirine... 

Monoalkylhydrazines can also be prepared by hydrolysis of diaziridines that are obtained from diazirines and Grignard reagents.287 Pentamethylenedi-azirine (2,3-diazaspiro[2.5]oct-2-ene)288 is a particularly suitable starting material for this synthetic route, which is of special value when the alkyl halide is more accessible than the amine. 

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