A-Diazoacetophenone

Halofluonnation of a-diazoacetophenone by N halosuccmimides in hydrogen fluonde-pyndine provides good yields of a-fluoro-a-haloacetopheiiones [6] (equation 24)... 

Cyclization-cycloaddition of an a-diazoacetophenone. Reaction of 1 with Rh2(OAc)4 in C6H6 at 25° results in 2 in 87% yield. This reaction is considered to involve a carbonyl ylide (a), which is trapped internally by the neighboring double bond.2... 

N itro-a-diazoacetophenone, AL74 -N i t ro-m-d iazoacetophenone, AL74 4 -N i t ro-2-d i azoacetophenone,... 

The success achieved with the Rh(II)-catalyzed transformations of -oximino diazo carbonyl compounds prompted our group to study some additional systems where the C-N 7i-bond was configurationally locked so that azomethine ylide formation would readily occur. Toward this end, we investigated the Rh(II)-catalyzed behavior of isoxazoline 186 in the presence of DMAD. This reaction afforded the azomethine-derived cycloadduct 187 as a 4 1 mixture of diastereomers in 65% yield. A similar transformation occurred using the a-diazoacetophenone derivative 188 which produced isoxazolo[3,2-a]isoquinoline 189 as a 2 1 mixture of diastereomers in 82% yield.84... 

Evans and co-workers have reported successful diazo transfer from p-nitrobenzenesulfonyl azide (PNBSA) to the enolate derivatives of an N-acyloxazolidinone and a benzyl ester (a) Evans, D. A. Britton, T. C. Ellman, J. A. Dorow, R. L. J. Am. Chem. Soc. 1990, 112, 4011. However, we have not been able to achieve efficient diazo transfer to ketone enolates employing these conditions. For example, exposure of the lithium enolate of acetophenone to 1.2 equiv of PNBSA in THF at -TS C for 15 min gave a-diazoacetophenone in only 21% yield. 

Dihydrofuran derivatives 319 are formed as major products in Rh2(OAc)4-catalyzed reactions of a-diazoacetophenone with 2-methoxy-propene or a-methoxystyrene (84MI1). Copper chelate or rhodium(II) acetate-catalyzed 1,3-dipolar cycloaddition of metal carbenoids, generated from ethyl formyldiazoacetate (90JOC4975), ethyl diazopyruvate... 

Molybdenum hexacarbonyl, when employed in catalytic amounts, effectively promotes cyclopropanation of acrylonitrile, methyacrylonitrile, and ethyl acrylate by ethyl diazoacetate and a-diazoacetophenone the intermediacy of molybdenum-carbene species in the formation of cyclopropane derivatives is suggested. 

WofS rearrangement (Amdt-Eistert reaction. The reagent has been used in acetonitrile-methanol to effect homogeneous rearrangement, for example of a-diazoacetophenone. After standing for several hours at room temperature, methyl phenylacetate is obtained in good yield. 

There has been continued interest in the synthesis of oxazoles from a-diazo carbonyl compounds and nitriles catalyzed by Lewis acids. The BFa-catalyzed reaction of a-diazoacetophenones or methyl p-nitrophenyldiazoacetate with chloroacetonitrile affords 5-aryl-2-chloromethyloxazoles or 2-chloromethyl-5-methoxy-4-(p-nitrophenyl)oxazole, respectively (Equation (19)) <89BCJ618>. The former products react with primary, secondary, and tertiary amines by nucleophilic displacement of the chloride group. Methyl or ethyl isocyanate may be used as the nitrile component to prepare... 

A rhodium-catalyzed decomposition of a-diazoacetophenones in benzonitrile gives an intermediate acyl-substituted nitrile ylide (157) that cyclizes to the oxazole or may be trapped with DMAD to produce a pyrrole (Scheme 73) <92CL2197>. Ethyl cyanoformate and ethyl 3,3,3 trifluoro-... 

Aromatic a-diazoketones can be prepared from 1 equivalent of CH N2, instead of the 2 equivalents usually used, by addition of triethyl-amine. The results with aliphatic compounds were less encouraging. —E A soln. of p-methoxybenzoyl chloride in ether added to a well stirred, ice-salt cooled soln. of diazomethane and triethylamine in ether during 20 min., and stirring continued in the cold for 12 hrs. —y p-methoxy-a-diazoacetophenone. Y 73%. (M. S. Newman and P. Beal, 3rd., Am. Soc. 71, 1506 (1949) s. a. M. Berenbom and W. S. Fones, Am. Soc. 71, 1629 (1949).)... 

Diazoalkane decomposition. Surprisingly, tetraphenylethylene is almost as efficient as various copper catalysts for decomposition of diazoalkanes to car-benoids. For example, diazomethane and cyclohexene in the presence of this catalyst react to form norcarane in 15 5% yield with copper catalysis the yield of norcarane is 24%. Cyclopropanations have been observed with this hydrocarbon catalyst with a variety of diazo compounds diazomethane, a-diazoacetophenone, and diazofluorene. Diphenyldiazomethane, however, is converted mainly into benzophenone azine, (C5H5)2C=NN=C(C6Hs)2. 

Diaza-Dewar benzene, 56 3H-1,2-Diazepines, 599 Diaziridines, 253 a-Diazoacetophenone, 577 Diazoalkanes, 514, 577... 

The large variety of products related to photolysis and thermal dediazoniations of diazo ketones is documented in a recent investigation of Padwa et al. (1993 b) of alk-2-enyl- and alk-2-ynyl-substituted a-diazoacetophenones. Thus, the photolysis of a-diazo-2-ethenylacetophenone (8.69) resulted in the formation of 2-naphthol (8-37,... 

The related 2-alkynyl-substituted a-diazoacetophenone derivative 8.72 gives the corresponding naphthol derivative 8.73 (8-38). This is, however, only the case if the... 

Another 1,3-dipole with properties that are representative for such compounds (see Sect. 6.2) is 8.150, which can be obtained by [Rh2(OCOCH3)4] catalysis from the a-diazoacetophenone derivative 8.149 (Padwa et al., 1988a). The 1,3-dipole reacts easily in an intramolecular fashion to form the tetracyclic compound 8.151. The dipole can, however, be trapped by dimethyl ethynedicarboxylate and the tricyclic compound 8.152 is isolated. 

The a-diazo ketone produced in this case has the name a-diazoacetophenone. 

Lewis acids efficiently catalyze the transfer of diazoketones and diazoesters to amides and nitriles to furnish 2,4,5-trisubstimted oxazoles (Scheme 1.49). In particular, Eguchi and co-workers found that BF3 OEt2 was the best catalyst for reaction of the adamantyl diazoketoester 180 with acetonitrile. Attempts to prepare 181 using Rh(II)acetate or photolysis were unsuccessful. Similarly, Ibata and Isogami °° described a general synthesis of 5-aryl-2-(chloromethyl)oxazoles 183 from a BF3.0Et2-catalyzed addition of a-diazoacetophenones 182 with chloro-acetonitrile. The yields were quite respectable (Table 1.12). 

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