Diazo compounds ketones, cyclic

B. Ring expansion of cyclic ketones using diazo compounds... 

Substitution of the acetate group at the C-3 position of the /3-sultam 105 can occur by reaction with silyl enol ethers in the presence of zinc iodide or zinc chloride. When the diazo compound is used, after desilylation with tetrabutyl-ammonium fluoride (TBAF), photochemical cyclization gives the bicyclic /3-sultam 106 as a mixture of two cis/ fra -diastereoisomers. When silyl enol ethers derived from cyclic ketones are used, the substitution product is stabilized by a retro-Michael-type reaction leading to open-chained sulfonamides 107 (Scheme 31) <1997LA1261>. 

One more carbene-based route to oxapenam derivatives utilizes the Cu-catalyzed decomposition of diazo compounds 547 via cyclic sulfonium ylide 548. The protocol is effective for 5-aryl (80H1999) and 5-heteryl-substituted (82H1597) diazo compounds of type 547. Oida and co-workers succeeded in obtaining oxapenam 549 (33%) by Cu(acac)2-catalyzed transformation of 5-alkenyl-substituted diazo ketones 550. The attempted synthesis of... 

Aliphatic diazo compounds react readily with aldehydes and ketones to produce ketones of higher molecular weight.25 With cyclic ketones the... 

Cyclic ketones are converted smoothly to diazo ketones in the presence of HMPA. 4-Nitrophenyl azide (128) exhibits a diazo transfer reaction with malonates and cyclic 1,3-cyclohexanedione (128) in some cases diazo compound 129 further leads to fused triazole derivative (130) formation.52... 

Lebedev (1991) published an extensive review on the mass spectrometry of diazoalkanes, diazo ketones, diazo esters, cyclic diazo compounds (including diazo-quinones), and related compounds. 

Scaiano et al. (1989) characterized the parent benzoquinone oxide, various derivatives thereof being obtained from the corresponding cyclic diazo ketones as well as from 9-diazofluorene, and from diazodiphenylmethane by laser flash photolysis at room temperature. The parent benzoquinone oxide has an absorption maximum at 410 nm. The rate constants of 2-diazo-l,2-benzoquinone and of the carbene of this diazo compound with singlet oxygen were found to be 1.0 x 10 m s and... 

C. Ring Expansion of Cyclic Ketones with Diazo Compounds... 

These reactions involve addition of the diazo ester to an adduct of the carbonyl compound and the Lewis acid. Elimination of nitrogen then triggers migration. Triethyloxonium tetrafluoroborate also effects ring expansion of cyclic ketones by ethyl diazoacetate.83... 

Fig. 14.29. Preparation of an a-diazoketone (compound E) from a ketone (A) and subsequent Wolff rearrangement of the a-diazoketone. Initially, A is transformed to give the enolate B of its a-formyl derivative. In a Regitz diazo group transfer reaction, this will then be converted into the a-diazoketone E. Ring contraction via Wolff rearrangement occurs and the 10-membered cyclic diazoketone C rearranges in aqueous media to give the nine-membered ring carboxylic acid E via the ketene D.

The Mukaiyama-Michael addition of silyl enolates to a, -unsaturated thioesters is promoted by an SbCl5-Sn(OTf)2 binary catalyst to afford d-keto thioesters with high anti selectivity (Scheme 14.23) [60]. The successive treatment of lactones with a ketene silyl acetal and silyl nucleophiles in the presence of an SbCl5-Me3SiCl-Snl2 ternary catalyst yields a-mono- and a/ -disubstituted cyclic ethers (Scheme 14.24) [61]. SbFs promotes the condensation of a,y5-unsaturated aldehydes and ketones with a-diazo-carbonyl compounds to give cyclopropane derivatives in high isomeric purity [62]. 

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