From diazo ketones

The first /3 -lactam was produced by addition of a ketene to an imine and there are now many examples of this type of approach. The ketenes are most frequently generated in situ from acid chlorides by dehydrohalogenation, but have also been produced from diazo ketones, by heating of alkoxyacetylenes and in the case of certain cyanoketenes by thermolysis of the cyclic precursors (162) and (163). 

A simple synthesis of a-amino ketones and esters 231 (R1 = EtO or Ph R2 = H or CO2EE R3 = Me or CH2C02Et R4 = PhCH2 or CH2C02Et) proceeds from diazo ketones and esters, respectively, tertiary amines and copper powder. The intermediate... 

Dinuclear Rh(II) compounds are another class of effective catalysts (227). Electrophilic carbenes formed from diazo ketones and dimeric Rh(II) carboxylates undergo olefin cyclopropanation. Chiral Rh(II) carboxamides also serve as catalysts for enantioselective cyclopropanation (Scheme 95) (228). The catalysts have four bridging amide ligands, and... 

The synthetic applications of 1,3-dipolar cycloaddition of carbonyl ylids generated from diazo ketones have been reviewed with particular focus on pseudolaric acids.12... 

The bicyclic product 59 proved not to be derived from diazo ketone 58. It may arise from the reaction of diazenyl ketene intermediate 53 with diazomethane via the postulated 2-[2-methyl-2-(phenyldiazenyl)propyl] cyclopropanone intermediate 60 and its subsequent isomerization to the bicyclic product 59 (Scheme 14). The formation of the diazenyl ketene intermediate 53 has been made plausible by carrying out the reaction in the presence of an excess of isobutyl alcohol to afford isobutyl 3-methyl-3-[(E)-phenyldiazenyl]butanoate (61) in a competing addition. 

Carbenoids, derived from diazo ketones RCOCN2R (R = R = Ph R = Me, R = Ph R = Ph, R = Me) react with enaminones to give pyrroles, e.g., 144. The mechanism presumably involves the electrophilic attack of a keto carbenoid on N and/or at the C-a-position of an enaminone system, followed by cyclization and loss of water (88JOC2084). 

Maas and co-workers have elaborated the approach to l-oxa-2-silacyclo-pentene derivatives based on cyclization of a siloxyalkylidenecarbene. Thus, as a result of intramolecular aliphatic C — H insertion of the carbene derived from diazo ketone 576, l-oxa-2-sila-4-cyclopentenes 577 were obtained in high yields. Here, the insertion may occur in primary, secondary, and tertiary C—H bonds (87CB635 94JOM115). When no C—H bond is adjacent to the Si atom, as in substrate 578, the cyclopropanation of a benzene ring with concomitant ring expansion may result in oxasilacyclopentene 579 (86CC1782). Photolysis or catalytic decomposition of bissilanes 580 furnishes fused bicyclic heterocycles 581 in moderate yields (90JOM229). 

The Rh2(OAc)4-catalyzed N —H insertion of carbenoids derived both from diazo ketone 591 (R = H, R = Me) and from diazo ketone 591 (R = Ac, R = PhCH20C0) furnishes the corresponding 1,4-oxazines in... 

Table 15. l-Acyl-2-oxycyclopropanes from Diazo Ketones and Enol Ethers or Enol Acetates or O-Silyl Enols... 

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). 

Dichloro and, a -dibromo ketones are obtained, for example, by the action of chlorine or bromine, respectively, on solutions of the diazo ketones in CC14 1185 and a,oc-diiodo ketones are obtained from diazo ketones and iodine in CHC13.1186 1187... 

Dipolar additions of carbonylcarbenes are closer to diazo chemistry, because carbonylcarbenes are formed from -diazo ketones. Carbonylcarbenes are... 

Other azomethine imines of a general formula 317, formed from diazo ketones 316 and TADs, are not isolable but can be trapped by alcohols to form the corresponding urazole derivatives, e.g., 318 (81TL2535). 

Fig. 3.4 Comparison of peroxy acid oxidation of an alkyne with the analogous reaction of a diazo ketone. The relative yields of products from alkyne and from diazo ketone (italics) are shown. The similarities and difference between such reactions has been ascribed to various possibilities (see text)...

Heterocycles by Cycloadditions of Carbonyl Ylides Generated from Diazo Ketones... 

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