Diazomethane with aromatic rings

The reaction of substituted diazomethanes with ethyl Ai-nitrocarbamate, followed by hydrolysis of the ethyl N-alkyl-N-nitrocarbamate, has been used to prepare some primary arylnitramines where aromatic ring nitration is not required, and so limits the use of conventional N-nitrating agents.The method has not been fiilly investigated. 

Cyclization of a thiocarbonyl ylide with the C=C-bond of an aromatic ring was observed in the reaction of aryl biphenyl-2-yl ketones with di(tosyl)diazomethane in the presence of Rh2(OAc)4 (189). In the case where the aryl ring contains a 4-methoxy group, benzo[c]thiophene (164) was the only product formed. In contrast, when the aryl ring consists of a 2,4,6-trimethylphenyl group, compounds 165 and 166 were produced. It would seem that after 1,5-dipolar electrocyclization of the intermediate thiocarbonyl ylide occurs, aromatization then takes place by elimination of toluenesulfinic acid or methyl toluenesulfinate. 

In the light-induced reactions with diazoalkanes, methylene, the photolytic fragment from diazomethane, may be interposed between the halogen atom in the organic halide and the carbon atom to which it is attached,289 290 or may add to the double bonds in the aromatic ring.58 69... 

The chemistry of benzo[Z>]furan-2(3//)-one (395) which exists in the keto form, is that expected of the lactone of 2-hydroxyphenylacetic acid. Grignard reagents bring about the expected ring opening. Condensations may be effected at the 3-position, especially with aromatic aldehydes. Methylation with iodomethane and potassium carbonate in DMF furnishes the 3-methyl and the 3,3-dimethyl compound. Methylation, with diazomethane,... 

Ring expansion of aromatic compounds by carbene, carbethoxycarbene, chlorocarbene, and carbenoid is well known 256, 336, 351-356). Muller and co-workers reported the reaction of aromatic compounds with carbene generated from a catalytic decomposition of diazomethane with copper salts, and proposed a bimolecular two-step mechanism involving an inverse ylid for the reaction. Miller (336) proposed another bimolecular two-step mechanism for the reaction of benzene with alkylcarbenoids of aluminum. Baldwin and Smith (25) proposed a concerted mechanism for the reaction of aromatic compounds with carbethoxycarbene. Reaction of alkylbenzene with diethylzinc and ethylidene iodide gives 7-methylcyclohepta-l,3,5-triene derivatives in yield 369). The... 

Analytical data indicate the presence of two aromatic rings in apogalanthamine, and the success of this reaction may result from the additional driving force provided by this aromatization. With diazomethane, apogalanthamine formed a dimethyl derivative and a small amount of an uninvestigated base, C17H19NO2, m.p. 205-207°. Perman-... 

As with other diazoalkanes, diazomethane reacts with alkenes to form cyclopropane derivatives (sec. 13.9.C.i).272 Reaction with aromatic derivatives leads to ring expansion to cycloheptatriene derivatives.223 Both of these reactions (addition to an alkene or arene insertion) involve generation of an intermediate carbene and addition to a jt bond they will be discussed below. Many of the reactions of diazomethane tend to be ionic in nature and are, therefore, set aside from the other diazoalkane chemistry in this section. One of the commonest uses of diazomethane itself is esterification of small quantities of acids, especially acids that are precious for one reason or another. The reaction is quantitative and gives good yields of a single product, as in Tadano s conversion of 338 to the methyl ester of 339224 in a synthesis of (-)-verrucarol. 

Diazomethane derivatives substituted by two aromatic rings (e. g., diphenyldiazo-methane) or fused aromatic systems (diazofluorene, diazoacenaphthenone) decompose analogously, but with rate-limiting protonation (as shown by general acid catalysis see, e.g.. More OTerrall et al., 1964). 

In addition, phenolic hydroxyl adjacent to a carboxyl group on an aromatic ring constitutes the major entity responsible for the chelation of metals in coal, particularly in the lower-rank coals. Phenolic hydroxyl is also determined by reaction with diazomethane (CH2N2) to form the methoxyl group (-OCH3) with the release of elemental nitrogen. 

Hay and Harris 153,157) have reported a biogenetic-type synthesis of lichexanthone (Scheme 14). To circumvent problems arising from numerous cyclisation pathways of a long polyketide chain these workers chose a starting compound with a pre-formed aromatic ring (132). Claisen condensation of the polyketide side chain of (132) in aqueous potassium hydroxide yielded a mixture of the benzophenone (133) and 3-0-methylnorlichexanthone (134). The benzophenone (133) could be converted into (134) by treatment with methanolic potassium hydroxide. Subsequent O-methylation of (134) with diazomethane yielded lichexanthone (135). 

Saito et al. <1995S87> described a new method for the synthesis of heterocycle-fused[c]thiophenes via reaction of aryl heteroaryl thioketones with the carbene precursors. Heteroaromatic thioketones A react with carbenoids generated from bis(arylsulfonyl)diazomethanes or phenyliodonium bis(phenylsulfonyl)methylides to give heterocycle-fused[f]thiophenes B. The reaction involves the ring closure of the intermediary thiocarbonyl ylides, followed by restorative aromatization via the elimination of a sulfenic acid (Equation 11). 

The photolysis of aromatic species with tetranitromethane in perfluoro alcohol solvent has been studied, in which the radical cations were observed by EPR spectroscopy.284 Photo-stimulated reaction of 1- and 2-haloadamantanes and 1,2- and 1,3-dihaloadamantanes with various carbanionic nucleophiles afforded products rationalized through an SrnI mechanism.285,286 Photolysis of the cycloadduct formed between a functionalized derivative of ( , and diazomethane has been shown to afford a pair of ring-opened structures (125) and (126) via a proposed biradical intermediate (127) (Scheme 19). The UV-photolytic fragments of /-butyl iodide (T and /-Bu ) have been ionized by resonance-enhanced multiphoton ionization for TOF mass spectro-metric analysis.287 A two-dimensional position-sensitive detector provided angular distribution and translational energy data. 

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