Diazocarboxylic ester

Catalytic decomposition of diazocarboxylic ester 198b with an allyl-coordinated PdCl2 yielded almost quantitatively thiopyranylidene ester 202 (82CL1843). Analogous phosphorus derivatives 204a and 204b were... 

The following are examples of other generation methods of the same kind of reactive sp2 carbon-centered radicals. Treatment of aromatic diazocarboxylate ester (11) at pH 7.2 forms the phenyl radical, through hydrolysis of the ester, decarboxylation to the phenyldiimide, and finally, reaction with molecular oxygen (eq. 11.9a). Electron transfer reduction of 1,4-diazonium (12) with Cu+ generates the corresponding /7-phenylene biradical (probably step-by-step formation) (eq. 11.9b). These simple sp2 carbon-centered radicals also destroy DNA plasmid at pH 7.6, under living-body conditions, like esperamicin [37-39]. 

Diazocarboxylate esters can be transformed by transition metal catalysts such as rhodium(II) acetate into alkoxycarbonylcarbenes that undergo a wide variety of synthetically useful C-H, C-C, C-X, X-H and X-X insertion reactions (where X = heteroatom) [99]. Chemoselectivity of rhodium carbenoids derived from Rh(II) carboxylates and carboxamides has been found to exhibit striking ligand dependency, for example in work by Padwa showing that perfluorocar-boxamide ligands exclusively promoted aromatic C-H insertions in Rh(II)-cat-alyzed decomposition of diazoamides to give oxindoles, whereas a carboxylate-based rhodium catalyst promoted other types of insertions and addition reactions [100]. 

Hydrazine appears to attack the a-carbon atom of 2-diazocarboxylic esters to give a new fused pyridazine with simultaneous elimination of hydrazoic acid. 

Monohalo or dihalo alkanes, carboxylic acids, or ketones are obtained on treating diazoalkanes,1167 diazocarboxylic esters,1168 or diazo ketones with hydrogen halides or halogens. The reaction usually occurs at room temperature or below. However, preparative importance attaches only to the formation of the halo ketones from diazo ketones they are obtained free from isomers (cf. page 189). 

S-Oxo-a-diazocarboxylic esters (40) are transformed into 1,2,3-thiadiazoles (41) (eq 33). These represent the valence tautomers of the corresponding a-diazo- 8-thioxo esters, which, however, cannot be detected as the intermediate products. ... 

Triazoles and a-diazocarboxylic acid esters from (a-acylalkylidene)phosphoranes N-Detosylation... 

Acj-nitro-esters (158), formed from alcohols (RCH2OH) and 2,6-di-t-butyl-4-nitrophenol using diazocarboxylate-PPhs as dehydrating agent, react with... 

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