Phenyldiazomethane, decomposition

Reaction of 5-imino-l,3-dipheny]-4-thioxoimidazo]idin-4-one with phenyldiazomethane is claimed to afford 4,5,7-tripheny]-l,4-dihydroimidazo[4,5-d]-l,2,3-triazin-6-one.217 However, this structure is probably a misinterpretation of phenyldiazomethane decomposition products.367... 

Aziridines have been synthesized, albeit in low yield, by copper-catalyzed decomposition of ethyl diazoacetate in the presence of an inline 260). It seems that such a carbenoid cyclopropanation reaction has not been realized with other diazo compounds. The recently described preparation of 1,2,3-trisubstituted aziridines by reaction of phenyldiazomethane with N-alkyl aldimines or ketimines in the presence of zinc iodide 261 > most certainly does not proceed through carbenoid intermediates rather, the metal salt serves to activate the imine to nucleophilic attack from the diazo carbon. Replacement of Znl2 by one of the traditional copper catalysts resulted in formation of imidazoline derivatives via an intermediate azomethine ylide261). 

Diazo compounds are usually easy to synthesize and handle if the N2 group is next to a carbonyl or an aryl group. In other cases, especially when electronreleasing substituents such as halogen or oxygen atoms are adjacent to the diazo moiety, diazirines prove to be more practical. Sometimes, diazirines undergo photorearrangement to diazo compounds prior to decomposition (or vice versa, as in the case of phenyldiazomethane" ), but this does not impede the formation of the desired carbene. 

Phenyldiazomethane shows no appreciable change on storage at -80°C for 3 months. Storage at -20°C led to significant decomposition after 2 weeks. 

For cyclopropanation of very electron-rich alkenes such as vinyl ethers copper(II) trifluoroacetate, copper(II) hexafluoroacetylacetonate or rhodium(II) acetate are the catalysts of choice. Copper trifluoroacetate catalysed cyclopropanation of vinyldia-zomethane with dihydropyran gives the corresponding vinyl cyclopropane adduct in low yield (equation 17). In contrast, catalytic decomposition of phenyldiazomethane in the presence of various vinyl ethers results in high-yield phenylcyclopropane formation (equations 18 and 19)27. 

The tandem reaction of carbenoids with simple imines to form azomethine ylides which then undergo 1,3-dipolar cycloaddition with various dipolarophiles was first reported in 1972.81 Treatment of phenyldiazomethane with copper bronze in the presence of excess N-benzylidenemethylamine resulted in the isolation of imidazoline 170. Formation of this product was rationalized by carbenoid addition onto the imine nitrogen to give azomethine ylide 169 which then underwent a 1,3-dipolar cycloaddition with another molecule of imine to produce the observed product. Bartnik and Mloston subsequently extended this observation by using other dipolarophiles.82 For example, catalytic decomposition of phenyldiazomethane and A-benzylidenemethylamine in the presence of dimethyl maleate or benzaldehyde gave pyrrolidine 171... 

Carbenes can be stabilized as transition metal complexes decomposition of phenyldiazomethane in the presence of a ruthenium(II) complex gives a carbene complex stable enough to be isolated and stored for months. These complexes are among the most important of carbene-derived reagents because of a remarkable reaction known as alkene (or more commonly olefin) metathesis. 

Other reactions involving the cleavage of a carbon heteroatom bond include a promising method for the deprotection of benzyl ethers by irradiation in the presence of acceptors (Scheme 46) [240-241] and the liberation of alkyl radicals (capable of initiating a polymerization) from alkyltriarylborate salts [242-243], The PET induced decomposition of phenyldiazomethane leads to cis-stilbene the reaction however appears to involve addition of the radical cation to a neutral molecule prior to nitrogen loss [244]. The detachment of a halogen after intramolecular electron transfer from the a C-X bond to an electron-rich... 

Oxirane, azirdine, and cyclopropane derivatives have also been prepared by the decomposition of phenyldiazomethane with Rh2(OCOCH3)4 in the presence of dimethylsulphide and an aldehyde and are described (2). 

Cycloheftatrienylidene 4). Unsubstituted 4 could be obtained by thermal or photochemical decomposition of tropone tosylhydrazone salt 19c) 35, 36), In the case of the dibenzo 19a) or tribenzo derivatives 19b), the diazocycloheptatrienes 20 a, b) could be isolated Then photolysis of 20 a, b gave 4 in these cases too. An interesting entry in the cyclohep-tatrienyhdene series consists of flash pyrolysis of phenyldiazomethane 21) followed by a rearrangement to 4 38). 

The thermal decomposition in acetonitrile is of intermediate order in phenyl-diazomethane between 1 and 2. Thus two reaction paths are operative, one uni-molecular leading to nitrogen and a carbene, and the other bimolecular, involving two molecules of phenyldiazomethane, viz. 

Photolytic decomposition of a diethyl ether solution of 3-methyl-3-phenyldiazirine (7) in the presence of A -methylmaleimide afforded cyclopropanated products 9 and 10 via an alkylcar-bene intermediate 8 by direct extrusion of nitrogen." Phenyldiazomethane was involved as an intermediate when the photolytic decomposition of 3-methyl-3-phenyldiazirine was carried out in the absence of solvent as shown by the formation of dihydropyrazoles as side products, in addition to cyclopropanated products. 

Arylcyclopropanes can be prepared from a variety of alkenes enamines react sluggishly, electron-rich alkenes are, in general, the most reactive. Thus, phenylcarbene, generated by dirhodium tetraacetate catalyzed decomposition of phenyldiazomethane, gave 2-butyl-1-phenyl-cyclopropane (2) in 6% yield from hex-l-ene, but l-butoxy-2-phenylcyclopropane (3) was obtained in 92% yield from butyl vinyl ether. ... 

A stream of ketene was passed into a stirred solution of phenyldiazomethane (11.8 g, 0.1 mol) and MeOH (5 mL) in CH2CI2 (200 mL) at — 70 °C under Nj atmosphere. In ca. 2 h the color gradually changed from red to yellow. Excess ketene and the solvent were removed in vacuo and the yellow, solid residue was recrystallized (CCIJ to give colorless crystals yield 14 g (85%). The product can be stored at — 30 C under N2 for several months without decomposition. 

Binuclear Rhodium(ll) Catalysts. Soon after the first report of dirhodium(ll) carboxylates 1 (Scheme 1) as effective catalysts for diazo decomposition in 1973 (21), this type of complex was discovered to actively catalyze cyclopropanation (22). Comparison of relative reactivity and stereoselectivity of catalyst 1 (R = CHs) and a stoichiometric carbene complex of (COsWCHPh for cyclopropanation of alkenes with phenyldiazomethane showed rhodium carbene involvement in the rhodium-catalyzed cyclopropanation (23). Catalyst 1 (R = CH3) also demonstrated improvement of cyclopropane production can be achieved by decreasing the available concentration of the diazo compound with a slow addition method (24). 

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

Lithium bromide catalyses the decomposition of phenyldiazomethane in ether at room temperature to give stilbene (68%) consisting almost exclusively of the Z-isomer. It is postulated that this remarkable stereoselectivity results from an intermediate in which two lithium ions are sandwiched between two molecules of phenyldiazomethane. In a related study it was shown that formation of the Z-stilbene is also favoured (up to 71%) when the same decomposition is catalysed by copper perchlorate or copper bromide in acetonitrile. ... 

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