Diazo compounds oxiranes

The addition of diazo compounds generally leads to three membered tings, although in special cases, linear adducts with an intact diazo group [110] or l,3,4-oxadiazol-3-ines [111] can be isolated Most diazo compounds are unstable and yield oxirans and aziridines [112,113,114] Aziridines are obtained exclusively on reaction of certain polyfluorinated acyl imines with diazomethane [115]... 

Polyfluoroalkyl- andperfluoroalkyl-substituted CO and CN multiple bonds as dipolarophiles. Dmzo alkanes are well known to react with carbonyl compounds, usually under very mild conditions, to give oxiranes and ketones The reaction has been interpreted as a nucleophilic attack of the diazo alkane on the carbonyl group to yield diazonium betaines or 1,2,3 oxadiazol 2 ines as reaction intermediates, which generally are too unstable to be isolated Aromatic diazo compounds react readily with partially fluorinated and perfluorinated ketones to give l,3,4-oxadiazol-3-ines m high yield At 25 °C and above, the aryloxa-diazolines lose nitrogen to give epoxides [111]... 

Different competitive processes are dependent on the diazo compound, on the unsaturated system, and on the solvent. With 1,1,1-trifluorobutan-2-one and diazomethane, the corresponding oxirane is formed almost exclusively. While methyl trifluoropyruvatc reacts with diazomethane to provide a mixture of the oxiranes, reaction of the pyruvate with ethyl diazoacetate provides a stable [3-1-2] cycloadduct.Chiral fluoroalkyl-substituted /i-oxo sulfoxide (e.g., 1) readily react with diazomethane to provide the corresponding chiral epoxides. Use of methanol as solvent favors oxirane formation over the competitive enol ether formation. 

Some examples of the preparation of oxiranes, thiiranes and aziridines by the reaction of diazo compounds with trifiuoromethyl-substituted carbonyl161 - 164 and thiocarbonyl compounds,165 imines,166167 and oximes168 arc known. However, as noted in Section 2.1.1.6.2.5.1., carbenes are not always the reactive species. Thus, the reaction can consist of a 1,3-di polar cycloaddition, followed by decomposition of the resulting pyrazoline. 

The most salient commonality among the 210 carcinogens that are positive in Salmonella is the electrophilicity that is intrinsic to the molecule or introduced by enzymatic modification. The former can be thought of as ultimate mutagens and include known or presumable alkylating and acylating agents diazo compounds, nitrosamides, nitrosoureas, dimethylcarbamyl chloride, diaryl alkynyl carbamates, aziridines, oxiranes, thiirane,... 

Diene syntheses with Mannich bases a-Spiroketones s. lA, 824 Oxiranes from ketones and diazo compounds... 

Still two other possibilities (routes D and E) are open to compound I. These make use of the rupture of the third bond of the oxirane function (the C-C bond) and the ambiphilic nature of the versatile diazo carbon. 

The reaction between diazomethane and 3-oxo-steroids is catalysed by alu-mina. The 5 -3-ketone gave a 5 -A-homo-4-one, and the 5a-compound afforded an oxiran (50%) and A-homo-ketones. [The unusually high proportion of oxiran here, implying the intermediate with an equatorial diazomethyl group, probably results from an anti-conformation of the diazo- and hydroxy-groups... 

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