Diazo alkanes compounds

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]... 

O-Alkylation of carbonyl compounds with diazo alkanes... 

Enol Ethers and Esters 0-15 O-Alkylation of carbonyl compounds with diazo alkanes 0-17 Transetherification 0-20 Reaction between acyl halides and active hydrogen compounds 0-23 Transesterification 0-24 Acylation of vinylic halides 0-94 Alkylation with ortho esters 0-107 O-Acylation of 1,3-dicarbonyl compounds... 

A neutral diazo compound can be considered as both a nucleophile and an electrophile. Thus, it can be substituted by the combination of an electrophilic moiety and a nucleophilic moiety (X+ Nu ") (Scheme 8). In practice, the diazomethyl group is transformed to the fluoromethyl group by treatment with hydrogen fluoride/pyridine mixture (70 30 w/w) (X = H Nu = F), or to the halofluoromethyl group by addition of A-halosuccinimide in the same medium (X = Cl, Br, I Nu = F), e.g. formation of l.16 The reaction can be performed on secondary diazo alkanes, diazo ketones or diazo esters.16 90 316... 

From the three direct [2 + l]-cycIoaddition routes, path a employing electronrich olefins and acceptor-substituted carbenes is the most efficient one, since the alkenes can be synthesized from carbonyl compounds or other precursors and the carbenes are produced from easily available diazo alkanes. Therefore this very flexible mode to construct donor-acceptor substituted cyclopropanes is by far the most frequently used route. 

The importance of a-diazo ketones as synthetic intermediates has led to the development of a number of general methods for their preparation.5 Particularly popular approaches include the acylation of diazo alkanes and the base-catalyzed "diazo group transfer" reaction of sulfonyl azides with 8-dicarbonyl compounds.6-7 While direct diazo transfer to ketone enolates is usually not a feasible process,8-9 diazo transfer to simple ketones can be achieved in two steps by employing an indirect deformylative diazo transfer strategy in which the ketone is first formylated under Claisen condensation conditions, and then treated with a sulfonyl azide reagent such as p-toluenesulfonyl azide.6a,6c,9,i0,11... 

Carrie et al. have reported several more cycloadditions of diazo-alkanes to activated olefins. Diazomethane reacts with /3/ -disubstituted-a-acylacrylic esters and nitriles and with 1,1-diacyl- or I-acyl-l-cyano-olefins to give substituted 1-pyrazolines (88). When the 3-acyl substituent is acetyl, isomerization to JV-acetyl-2-pyrazolines (89) may occur. Thermolysis of some of these compounds gives olefins, cyclopropanes, and dihydrofurans. 

An intermediate organic nitroso compound RNO/ is formed, leading to N2 during its decomposition [1-5]. The mechanistic studies by Sachtler and co-workers [1 1] for the reduction of NOx by light alkanes over Fe/ZSM-5 involved adsorbed RNOx species which further react with gas-phase NOx to produce N2, through the decomposition of diazo compounds [2,4],... 

Complexes were also considered for other carbenes and even suggested for reactions in alkane solution( ) A counterproposal, backed by the inability of theory to find support for such stable complexes, held that the second source was not the carbene-alkene complex but instead was the diazo compound, formed from isomerization of excited diazirine. " Other LFP studies reinforced the need for two intermediates, but could not finally resolve the question of carbene complexes ver-sus diazo compound. However, the question is now settled in this case,... 

Organic compounds Organic fluorine compounds arc made by reaction of the corresponding alkane chloro-compounds with silver fluoride, mercurous fluoride, antimony trifluoride, titanium tetrafluoridc. and the arene fluoro-compounds by the diazo-reaction using hydrogen fluoride, and otherwise. The effect of the continued replacemenl of hydrogen atoms by fluorine atoms is an initial increase in reactivity, followed by a reversal of this effect, so lhal the highly substituted compounds arc relatively inert, See also Fluorocarbon. 

Caibene reagents also functionalize alkanes. Triplet CH2 adds unselecdvely to alkane C—bonds. The product mixture obtained from n-pentane was found to be 48% n-hexane, 3S% 2-methylpentane and 17% 3-methylpentane, so that addition to a primary C—bond appears to be favored. Monochloro-methylcarbene, CHCl, is less reactive and more electrophilic and so the normal tertiary > secondary > primary selectivity pattern was observed. Ethoxycarbonylcarbene, formed on fdiotolysis of the corresponding diazo compound, inserts rather unselectively in to alkane C—H bonds to give the ethoxycarbo-nylmethyl derivatives in ca. 50% yield. Transition metals, such as copper(II) or rhodium(I). also usefully catalyze the insertion of carbenes into alkane C—bonds. 

Finally, we note that deamination could in principle be achieved by generating an aliphatic diazonium ion in the presence of a hydride source this could lead to an alkane either via the diazene, or by Sn2 attack with loss of N . Protonating an aliphatic diazo compound, or treating an /V -alkyl, N -aryltriazene with protic or Lewis acid in the presence of a suitable reducing agent (NaBHsCN, NaBH(OAc)3 or RsSiH) might achieve this transformation. 

A cyclic iminocarbene was transferred from 2-diazo-5-isopropyl-3,6-dimethoxy-2,5-dihy-dropyrazine to an alkene under unusually mild conditions. This diazo compound decomposes under the conditions of its synthesis from 2,5-dihydropyrazine 8, and in the presence of cy-cloalkenes, 2,5-dihydrospiro[pyrazine]bicyclo[n.l.O]alkanes 9 (n = 3-5) were obtained (an experimental procedure is given in Houben-Weyl Vol. E19b, pi 194). 

The earliest examples of transition metal carbenoid C-H insertion reactions were carried out with ethyl diazoacetate 13 (EDA) and simple alkanes acting as the reaction solvent. In 1974, Scott and DeCicco reported that CuS04 and CuCl were capable of decomposing EDA in the presence of cyclohexane (14) to generate C-H insertion product 15 [13]. Although these results, along with control experiments, provided proof that the copper catalyst was necessary for the transformation to take place, the maximum yield of the product was only 24%, and dimeric byproducts of the diazo compound dominated, even at high dilution (Scheme 3). 

Methods for the Preparation of Alkane, Alkene, and Alkyne Diazo Compounds... 

---