3/f-Diazirine

Scheme 11 Photolysis Reactions of [3-(Trifluoromethyl)-3//-diazirin-3-yl]arenes and 3/f-Diazirin-3-ylarenes171...

Scheme 13 Synthesis of 4-[3-(Trifluoromethyl)-3/f-diazirin-3-yl]-D,L-phenylalanine According to Shih and Bayley[125l...

V-(9-Fluorenyhnethoxycarbonyl)-4-[3-(trifluoroniethyl)-3/f-diazirin-3-yll-L-phenylalanine [Fmoc-L-Phe(4-Tmd)-OH] (51) 129l... 

Diazirines, which on heating or irradiation are converted into carbenes either directly or via the corresponding diazo compound, have been infrequently employed for the preparation of monoarylcyclopropanes. One of the few reports involved 3-(l-naphthyl)-3/f-diazirine. When this compound was irradiated in a mixture of acetonitrile and acrylonitrile, carbene addition to the C-C double bond took place, yielding a mixture of cis- and /ranj-l-cyano-2-(l-naph-thyl)cyclopropane (1) together with the cis- and trans-isomers of 4-cyano-5-methyl-2-(l-naph-thyl)-3,4-dihydro-2//-pyrrole (2). ... 

Arylhalocarbenes are electrophilic species. This means that they readily undergo addition to electron-rich (nucleophilic) alkenes. Arylhalocarbenes also react with electron-deficient (electrophilic) alkenes, but at a slower rate these reactions are carried out with arylhalocarbenes generated from 3 f-diazirines. 

Experimental procedures for the preparation of 3-chloro-3-phenoxy-3/f-diazirine ° and 3-fluoro-3-methoxy-3//-diazirine are given in Houben-Weyl, Vol. E19b, p 1655 and 1656, respectively for the preparation of dimethyl 3-chloro-3-methoxycyclopropane-tra s-l,2-di-carboxylate, see Houben-Weyl, Vol. E19b, pl657. 

Decomposition of 3-chloro-3-methoxy- (25 °C, 24 and 3-chloro-3-phenoxy-3/f-diazirine (25 C, 72 in ring-substituted styrenes, gave c //ra Msomer mixtures of 2-aryl-1-chloro-l-methoxy(or -phenoxy)cyclopropanes 4. 

As the starting diazirines have now become readily available from the exchange of the halogen atom in a 3-halo-3-organooxy-3/f-diazirines for an alkoxy group, this method has gained importance. 

The fate of diazirines on decomposition can be influenced by the addition of /J-cyclodextrin (/J-CD). When 3-methyl-3-phenyl-3/f-diazirine (3) was thermolyzed under argon, l-methyl-1,2-diphenylcyclopropane (4) was obtained as an isomeric mixture in close to 20% yield the main product (43% yield) was acetophenone azine (5).72 Cyclodextrin complexation prior to pyrolysis, however, increased the yield of 4 tremendously. The carbohydrate, therefore, facilitates both styrene (6) and cyclopropane formation.73,74 It is also interesting to note that the trans-4j cis-4 ratio increased concomitantly and that styrene appears as an isolable product after photochemical, but not after thermal degradation of the 3 /J-CD complex.72... 

On the other hand, photolytic cleavage of 3-bromo-3-(4-trifluoromethylphenyl)-3/f-diazirine in hex-1-ene or 2,3-dimethylbut-2-ene gave the corresponding cyclopropanes in very low... 

Warning diazirines are explosive. All operations must be carried out behind safety shields. 3,3-Dimethoxy-3/f-diazirine 63... 

Chloro-3/f-diazirines are formed by oxidation of amidines with sodium hypochlorite ... 

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