Carboxamides rearrangement

Although iodine(III) reagents attack double bonds, the rearrangement of the amide group is, at least in some cases, more rapid than electrophilic attack on alkenes. Thus 3-cyclohexene-l-carboxamide rearranges smoothly to the corresponding amine as long as only one equivalent of [1,1-bis(trifluoroacetoxy)iodojbenzene is used. 

The recently reported rearrangement (1581) of 2-allylamino-4-carboxamido-5-aminothiazoIes to 4-aminoimidazole-5-carboxamide in presence of sodium bicarbonate probably involves the electrophilic reactivity of C-2, which allows the ring opening. 

Other methods for the preparation of cyclohexanecarboxaldehyde include the catalytic hydrogenation of 3-cyclohexene-1-carboxaldehyde, available from the Diels-Alder reaction of butadiene and acrolein, the reduction of cyclohexanecarbonyl chloride by lithium tri-tcrt-butoxy-aluminum hydride,the reduction of iV,A -dimethylcyclohexane-carboxamide with lithium diethoxyaluminum hydride, and the oxidation of the methane-sulfonate of cyclohexylmethanol with dimethyl sulfoxide. The hydrolysis, with simultaneous decarboxylation and rearrangement, of glycidic esters derived from cyclohexanone gives cyclohexanecarboxaldehyde. 

At low temperature a 1 1 adduct of thioacetic acid and an enamine could be prepared (709). The previously described reaction of aminomethylene ketones with hydrogen peroxide was extended to bisaminomethylene compounds. However, acylated cyclohexenamines led to cyclopentane-carboxamides (770), Trichloromethyl adducts of enamines and the rearranged amine derivatives were described in a further study (777). 

Cornforth reported in 1949 that 2-phenyl-5-ethoxyoxazole-4-carboxamide (3) rearranged on heating to ethyl 2-phenyl-5-aminooxazole-4-carboxylate (4). ... 

Dewar and Turchi carried out similar rearrangements of secondary and tertiary alkyl and aryl oxazole-4-carboxamides (5a-e) to the corresponding secondary and tertiary 5-aminooxazoles (6a-e). For example, they realized yields > 90% when the amide nitrogen is part of a heterocyclic ring system. 

A microwave assisted Comforth rearrangement of oxazole-4-carboxamides 106 efficiently afforded 5-aminooxazole-4-carboxylates 107. This procedure was applied to the formal synthesis of a natural antibiotic derived from pseudomonic acid <06TL4698>. 

Orthophosphoric and benzylphosphonic acids have been selectively alkylated with triethyl phosphite in a new synthesis of mono-, di-, and triethyl phosphates and of mono- and di-methyl phosphonates.62 A-Methylol carboxamides and sulphonamides react with trialkyl phosphites to give the phosphonate derivatives (78) and (80), respectively.63 However, the mechanism appears to be quite different in each case while the carboamides react by a transesterification-rearrange-ment pathway, the sulphonamides undergo elimination-addition via the imine (79). 

Photochemical Beckman rearrangement of oximes results in the formation of carboxamides as the major product151 (equation 92). 

New rearrangements of 2-imino-2//-l-benzopyran-3-carboxamides under the action of anthranilic acid as an N-nucleophile have been revealed. Depending on the conditions 2-(2-oxo-2//-l-benzopyran-2-yl)-3//-quinazolin-4-ones or 2-oxo-2//-l-benzo-pyran-3-((V-2-carboxyphenyl)carboxamides were found to be the products. 

The oxidative method using C6H5l(OAc)2 3uelded the desired quadricyclyl azide and the process is being scaled up. In another approach (Fig. 2.17), the hypervalent iodine Hoffmann rearrangement was carried out on quadricyclyl carboxamides. 

Rhodium(II) carboxylate dimers and their carboxamide counterparts have been demonstrated to be exceptionally useful catalysts for carbene transfer processes involving diazocarbonyl substrates [1]. Doyle s seminal work identified Rh2(OAc)4 as the catalyst of choice for a variety of cyclopropanation, C-H insertion, and ylide rearrangement transformations using diazoketones or diazoesters [2]. Important contributions by Taber [3], Padwa [4], and Davies [5] further established the superior catalytic activity of dirho-dium catalysts and the excellent selectivity of rhodium-[Pg.417]

A potential versatile route into a-amino acids and their derivatives is via a combination of (i) nitrile hydratase/amidase-mediated conversion of substituted malo-nonitriles to the corresponding amide/acid followed by (ii) stereospecific Hofmann rearrangement of the amide group to the corresponding amine. Using a series of a,a-disubstituted malononitriles 14, cyanocarboxamides 15 and bis-carboxamides 16, the substrate specificity of the nitrile hydratase and amidase from Rhodococcus rhodochrous IF015564 was initially examined (Scheme 2.7). The amidase hydrolyzed the diamide 16 to produce (R)-17 with 95% conversion and 98%e.e. Amide 17 was then chemically converted to a precursor of (S)-a-methyldopa. It was found... 

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