Benzene derivatives reaction with diazomethane

Hydroxypyridine (86, R = H) and its derivatives also belong to the class of heterocyclic enols. In benzene and dioxane, 3-hydroxy-pyridine occurs as the neutral molecule (and not as a betaine).Its reaction with diazomethane, in heterogeneous media, gives a mixture of 3-methoxypyridine (86, R = Me) (10%) and l-methyl-3-hydroxy-pyridinium betaine (87) (30%If tert-butanol is used as a... 

Thioamides of two cyclopropanecarboxylic acids undergo coupling reactions with diazomethane derivatives in refluxing benzene containing rhodium(II) acetate. The reaction conceivably takes place via a thiirane intermediate which undergoes reductive elimination by reaction with excess diazo compound. An example of an intramolecular reaction is the formation of indolizine 2. If the diazo compound is not in excess a thiol is formed, this can be removed by Raney nickel desulfurization. ... 

The methyl ester (100, R = CH3), derived from this A-nor acid by treatment with diazomethane, is different from the ester (102) obtained either by Favorskii rearrangement of 2a-bromo-5a-cholestan-3-one (101) or by the action of cyanogen azide on 3-methoxy-5a-cholest-2-ene (103) followed by hydrolysis on alumina. The ketene intermediate involved in photolysis of (99) is expected to be hydrated from the less hindered a-side of the molecule to give the 2j -carboxylic acid. The reactions which afford (102) would be expected to afford the 2a-epimer. These configurational assignments are confirmed by deuteriochloroform-benzene solvent shifts in the NMR spectra of esters (100) and (102). ... 

The effect of solvents on the reactions of lactams with diazomethane can be pronounced saccharin gives only A -methyl derivative in benzene solution, but in ethereal solution up to 24% of 0-methyl saccharin is formed in the still more strongly polar solvent di-... 

Reactions of 4,7-phenanthroline-5,6-dione have been the subject of considerable study. It is reduced to 5,6-dihydroxy-4,7-phenanthroline by Raney nickel hydrogenation226,249 or by aromatic thiols in benzene,262 and oxidized by permanganate to 3,3 -bipyridyl-2,2 -dicarboxylic acid.263 It forms bishemiketals with alcohols226 and diepoxides with diazomethane.226 The diepoxides by reaction with hydrochloric acid form diols of type 57, R = Cl, which on oxidation with lead tetraacetate give 3,3 -bipyridyl diketones of type 58, R = Cl. Methyl ketones of type 58, R = H, are also obtained by lead(IV) acetate oxidation of the diol 57, R = H, obtained by lithium aluminum hydride reduction of 57, R = Cl. With phenyldiazomethane and diphenyldiazomethane the dione forms 1,3-dioxole derivatives,264,265 which readily hydrolyze back to the dione with concomitant formation of benzaldehyde and benzophenone, respectively. 

A much more general method for acyl silane synthesis involving silyl diazo intermediates is illustrated in Scheme 1688. The lithiated derivative of trimethylsilyl diazomethane reacts smoothly with alkyl halides in THF solution to give a-trimethylsilyl diazoalkanes in good yields. Oxidative cleavage of the diazo moiety is effected using 3-chloroperbenzoic acid in benzene solution, to give access to a wide variety of acyl silanes in yields of up to 71%. A phosphate buffer (pH 7.6) is used to prevent side reactions. Aromatic acyl silanes clearly cannot be prepared by this chemistry since an aromatic nucleophilic substitution reaction would be required. 

On oxidation with Cr03, the 2-carboxy-derivative is readily obtained, which can be converted with diazomethane into the methoxycarbonyl analogue. The carboxy-compound gives an acid chloride with PC15 and a benzoyl derivative on Friedel-Crafts reaction with benzene.92... 

Dzhemilev et al. (1991) conducted an interesting investigation on the yield of cycloheptatriene formed in the reaction of benzene with diazomethane with various catalysts. The yield decreases in the presence of transition metal complexes in the series Rh-C (100<7o), Rh2(CF3COO)4 (57q/o), CuCl (39< o), CuBr (37<7o), Rh2(CH3COO)4 (17< o), activated charcoal (15 /o). Toluene, biphenyl, and dimethyl-benzenes yield mixtures of the corresponding regioisomeric cycloheptatriene derivatives in 82-98 yield. With naphthalene, cyclopropanation took place in the 1,2-position only (98< o). The benzonorcaradiene formed resisted isomerization to benzocycloheptatriene. 

It has been stressed that the presence in a benzene derivative of two bulky substituents, such as chlorines ortho with respect to the reaction site may cause severe steric hindrance. As expected, the perchloroaryl carboxylic acids are not esterified by Meyer s acid-catalysed procedure either, although their methyl esters are readily prepared with diazomethane (Riera, 1961). In general, the synthesis of alkyl esters is successfully performed by acylation of alcohols with the overcrowded acid chlorides, the latter being obtained smoothly from the corresponding acids with thionyl chloride. 

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... 

Photolysis of (aryl)(phosphoryl)diazomethane derivatives 1 in benzene gave mixtures of 1 1 (2) and 1 2 fraw.v-adducts (3), which were separated by column chromatography. Note that the copper-catalyzed reactions proceeded in poorer yield. Careful NMR studies have shown that the norcaradienes 2 are in valence tautomeric equilibria with the corresponding cyclohep-tatrienes 4, and that the phosphoryl group is always in the exo position. ... 

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