3- Phenyl-3- diazirine

One example has been reported in which fluorine is replaced by an N-nuclcophilc with the intermediacy of a carbene species. Thus, when 3-fluoro-3-phenyl-3//-diazirine (2) is irradiated in the presence of a secondary amine, a diaminophenylmcthanc derivative 3 is formed.19... 

With the intent to selectively derivatize CyD oligosaccharides,80 Abelt enlisted nitrogenous carbene precursors as labile guests.81 The involvement of supramolecular carbenes could be inferred based on intramolecular products stemming from 1,2-H shifts. Of course, 3//-diazirines that possess a-C-H bonds, like 3-methyl-3-phenyl-3//-diazirine (6) (Scheme 2), are susceptible to rearrangements in the excited state (RIES) that mimic the results of carbene 1,2-H shifts,82 e.g., 6 —>10 (Scheme 2). 

Similarly, photolysis of 3-fluoro-3-phenyl-3//-diazirine in 4-substituted styrenes, as well as 3-fluoro-3-(4-methoxyphenyl)-3//-diazirine in alkenes, resulted in the formation of 1-fluoro-1-phenyl-2-(4-substituted-phenyl)cyclopropanes 4 and 1-fluoro-1-(4-methoxyphenyl)cyclo-propanes 5 (in low yields), respectively. 

A mixture of 1-aryl-l-chlorodiazirine and an alkene in hexane sonicated with ultrasound (Fisher Scientific Solid State Ultrasound FS-9) at 40 °C for two hours afforded 1-aryl-l-chlorocyclo-propanes with yields similar to those obtained by photolysis. Electrophilic as well as nucleophilic alkenes were used. Photolytic, thermal or ultrasonic decomposition of 3-chloro-3-phenyl-3//-diazirine in 2-vinylpyridine did not give the corresponding 1-chloro-l-phenylcyclopropane derivative (see Section 1.2.1.3.1.2.2.1). 

However, 1-acetoxy-1-phenylcyclopropanes can be synthesized by photolytic reaction of 3-acetoxy-3-phenyl-3//-diazirine (obtained from the corresponding bromo-diazirine and tetrabutylammonium acetate), with an alkcne. Excellent yields of acetoxycyclopropanes were obtained from alkenenitriles, e.g. 5, while a rather poor yield was obtained from 2-methylbut-2-... 

Methoxy-2,2,3,3-tetramethyl-l-phenylcyclopropane [the addition product of methoxy-(phenyl)carbene, generated thermally or photolytically from 3-methoxy-3-phenyl-3//-diazirine, to 2,3-dimethylbut-2-ene] can be prepared in a low yield (in addition to a significant amount of azine) provided that the freshly purified alkene is used. The use of the commercial alkene leads exclusively to the formation of peroxyacetal, the product of the carbene reaction with 3-hydroperoxy-2,3-dimethylbut-l-ene which in turn results from oxidation of 2,3-dimethylbut-... 

To a solution of NaOEt (0.68 g, 10 mmol) in EtOH (10 mL), was added ethyl o-hydroxycinnamate (1.92 g, 10 mmol), and after dissolution of the phenolate formed, the mixture was taken to dryness. A solution of 3-bromo-3-phenyl-3//-diazirine (1.96g, 10 mmol) in dry hexane (17.3 mL) was added in one portion to a solution of the Na salt of ethyl 2-hydroxycinnamate in dry DMF (10 mL) under argon at rt. The mixture was stirred overnight. Normal workup (Et20, 1 M cold aq NaOH) and flash chromatography (hexane/EtjO 10 1.5) gave 2.28 g (82%) of the product as a colorless oil. 

For example, 3-bromo-3-phenyl-3//-diazirine was photolyzed with propenenitrile or... 

Several comparative studies are available in the literature, which clearly shows that, according to the latest results, tetrafluoro-pheny/ azides (AZ), trifluoro-methyl-phenyl diazirines (DZR), and particularly benzophenone (BP) are the best choice (Scheme 3.). Diazocarbonyl compounds, which played a historically role in the evolution of PAL, can also be considered together with aryl-diazonium salts [6] (not shown). For aryl azides the more common unsubstituted photophore is presented. It should be noted that tetrafluoro-phenyl azides have an increased reactivity towards CH-groups and they do not rearrange. Other substituted phenyl azides can readily alter the excitation wavelength allowing the application of milder or differential photoactivation. 

Figure 34 Panel of mannose-based photocross-linkers. The cross-linking activity of photoactive a-mannosides was compared in a simple model system. The trifluoromethyl phenyl diazirine yielded the most effective cross-linking to a variety of amino acids.

O-acyl thiohydroxamates was initially thwarted by competing ionic reactions but eventually culminated in the introduction of 3-bromo or 3-(trifluoromethyl)-3-phenyl diazirine as extremely effective reagents [27]. In contrast to almost all of the other reactions of Barton esters described in this chapter, however, the reaction sequence does not involve a chain process. Thus, as outlined in Scheme 25, capture of the alkyl radical by the diazirine is followed by dimerization and subsequent loss of nitrogen to give the product imine from which the desired amide or amine is easily liberated by mild hydrolysis. Some typical yields are shown in the Scheme 26. 

Scheme 6.16 (Photo)decomposition of phenyldiazomethane (37) and phenyl diazirine (37 ) yields phenyicarbene (39) that is in equilibrium with cycloheptatetraene (38) [50]...

Diazirine, 3-phenyl-3-chloro-rate constants, 7, 227 (80JA7576)... 

Scheme 176 represents the opposite situation, with stable phenyl azide used as a probe to trap very reactive and short living alkynes. Thus, diazirine 1064 generates cyclohexyne 1066 that is too reactive to be isolated and characterized. However, when phenyl azide is added to the reaction mixture, it traps species 1066 in situ to give triazole 1068 in 84% yield. Similarly, even more strained norbornyne 1067, generated from diazirine 1065, is trapped by phenyl azide to afford triazole 1069 in 22% yield <2006AGE309>. 

The synthesis reported by Nassal is based on the Ca-alkylation of diethyl 2-(ace-tylamino)malonate by 3-[4-(bromomethyl)phenyl]-3-(trifluoromethyl)-3//-diazirine (46) (Scheme 12) J122l The precursor for the diazirine-containing alkylating agent is 2,2,2-trifluoro-l-(4-tolyl)ethanone (39).1124 ... 

Scheme 14 Oxazolone-Mediated Tritiation of 4-[3-(Trifluoromethyl)-3/f-diazirin-3-yl]phenyl alanine11151...

Ethyl 2-[(Diphenylniethylene)aminol-3- 4-[3-(trifluoromethyl)-3//-diazirin-3-yl]phenyl)propanoate... 

Bromo-2-butyl-1 -(4-trifluorome-thyl-phenyl)- El7a. 570 (Br — Ar- 311 -diazirin + 1-Hexen)... 

The low-energy ionizations of 2-X, 3-X, 3,4-X2, 2,5-X2 and 2,3,4,5-X4 (X = Cl, Br, I) thiophen are correlated in Figures 24 a-c based on Hel/Hell ratio changes, band shape analyses, Penning ionization and CNDO/S calculations. The spectra of 3-phenyl-3-X-diazirines (X = Cl, Br or CF3) and 3,3-bis(trifluoromethyl)diazirine were studied by Kramarenko et al.m... 

Figure 2. Reaction of l-thio-(3-D-galactopyranose with MAD yielding N- m- 3-(trifluoromethyl) diazirin-3-yl] phenyl]-4-(-3-thio (-l-D-galactopyranosyl)-succinimidyl)butyramide (MAD-Gal) (after Y. Chevolot5).

D. Leonard, Y. Chevolot, O. Bucher, H. Sigrist, and H. J. Mathieu, Part I. 7V-[m-(3-(trifhioromethyl)diazirine-3-yl)phenyl]-4-maleimido-butyramide on Silicon, Silicon nitride and Diamond (MAD), Surf Interface Anal. 26, 783-792 (1998). 

---