Addition to diazoalkanes

Diazirine, fluoromethoxy-nitrogen extrusion, 7, 224 Diazirine, methylvinyl-rearrangement, 7, 221 Diazirines addition reactions to Grignard compounds, 7, 2 0 as carbene precursors, 7, 236 IR spectra, 7, 203 microwave spectrum, 7, 199 molecular spectra, 7, 202-204 nitrogen extrusion, 7, 223 NMR, 7, 202 photoconversion to diazoalkanes, 7, 234 photoisomerization, 7, 221 photolysis, 7, 225-227 quantum chemical investigations, 7, 197 reactions... 

Pertluoroallene is also quite reactive in its additions to nitrones [20], diazoalkanes [20] and sydnones [19] With sydnones, the isolated product derives from a fluoride ion rearrangement of the primary adduct (equation 21)... 

Tnfluoromethyldiazomethane behaves as atypical diazoalkane in its additions to carbon-carbon multiple bonds [9] For example, its reactions with ethylene and... 

Another class of nucleophilic addition to iminium salts can be found in the addition of diazoalkanes. These are of great interest since they were known to add and then reaet further to form three-membered rings as in the case of C=S, C=0, and C=C functions 103). Leonard and Jann 104-106) found that treatment of iminium perchlorates with diazomethane and other diazoalkanes yielded aziridinium salts. Treatment of an iminium salt such as N-cyclohexylidinepyrrolidinium perchlorate (66) with diazomethane yielded a new product whose structure was established by spectral and chemical means to be 5-azoniadispiro[4.0.5.1]dodecane perchlorate (67). The UV spectrum was devoid of any absorption above... 

In the case of the reaction between 2-diazopropane and diphenyldiacetylene, the reverse (as compared with other diynes) orientation of addition of the first molecule of the diazo compound with a predominant formation of 4-phenylethynylpyrazole is observed. Therefore, it is noteworthy that whereas the regioselectivity of the addition of diazoalkanes to alkenes is well studied audits products have, as a rule, the structure been predicted with respect to electron effects, the problem of orientation... 

Whereas the Rh2(OAc)4-catalyzed addition of diazoalkanes to propargyl alcohols readily gives the insertion of the carbene into the 0-H bond, with only a small amoimt of cyclopropenation of the resulting propargylic ether [54] the 2-diazopropane 59 reacts at 0 °C with l,l-diphenyl-2-propyn-l-ol 62a in dichloromethane and exclusively gives, after 10 h of reaction, only the adduct 63a isolated in 75% yield and corresponding to the regioselective 1,3-dipolar cycloaddition of the 2-diazopropane to the alkyne C - C bond (Scheme 15). 

The alkylation of acids with triazenes is superior to alkylation with diazomethane and other diazoalkanes in that the triazenes are crystalline, stable materials which are easy to prepare and store. Alkylations with triazenes are unlikely to be accompanied by side reactions, such as addition to strained or conjugated double bonds, which are frequently observed in alkylations with diazoalkanes. 

Transition metal complexes which react with diazoalkanes to yield carbene complexes can be catalysts for diazodecomposition (see Section 4.1). In addition to the requirements mentioned above (free coordination site, electrophi-licity), transition metal complexes can catalyze the decomposition of diazoalkanes if the corresponding carbene complexes are capable of transferring the carbene fragment to a substrate with simultaneous regeneration of the original complex. Metal carbonyls of chromium, iron, cobalt, nickel, molybdenum, and tungsten all catalyze the decomposition of diazomethane [493]. Other related catalysts are (CO)5W=C(OMe)Ph [509], [Cp(CO)2Fe(THF)][BF4] [510,511], and (CO)5Cr(COD) [52,512]. These compounds are sufficiently electrophilic to catalyze the decomposition of weakly nucleophilic, acceptor-substituted diazoalkanes. 

In the course of an extensive study of the chemistry of azo compounds, Overberger et al. [47a] prepared 1-pyrazolines, which may be considered cyclic azo compounds, by the addition of diazoalkanes to styrene. The reaction is considered a stereospecific 1,3-dipolar addition and, in the reaction between />-methoxyphenyldiazomethane and />-methoxystyrene both trans-3,5-bis-(p-methoxyphenyl)pyrazoline (m.p. 129°C, dec.) and c/s-3,5-bis(/>-methoxy-phenyl)pyrazoline were prepared and separated [47b]. 

Walling297 suggested that the electronic structure of the carbenes, the photolysis products from diazoalkanes, is somewhat analogous to carbon monoxide, and most of their subsequent reactions, e.g., addition to aromatic58 59 or rearrangements98 are those of electron-deficient electrophilic entities rather than radicals.51 However, radical photoaddition of diazomethane to carbon tetrachloride289 290 should not be overlooked. 

Electronic and steric factors seem to determine both the site and the orientation of addition of diazoalkanes to conjugated enynes. Although rates of addition of DPD to ethene and ethyne bearing identical single substituents are approximately the same,48 addition to butenyne occurs almost exclusively at the double bond.46... 

The characteristics of the 1,3-dipolar cycloaddition mechanism of azides and other 1,3-dipoles (such as diazoalkanes, azo-methine imines, nitrones, nitrile imines, nitrile oxides) have been described in detail by Huisgen.191 19 According to the author, the addition of a 1,3-dipole (a b c) to a dipolarophile (d e) occurs by a concerted mechanism in which the two new a bonds are formed simultaneously although not necessarily at equal rates (32). As a consequence, a stereoselective cis addition is observed. Thus, the addition of p-methoxyphenyl azide to dimethyl fiynarate (33) yields l-(p-methoxyphenyl)-4,5-froiw-dicarbomethoxy-AMriazoline (34),194 and 4-nitrophenyl azide gives exclusively the respective cis-addition products 35 and 36 on addition to irons- and cis-propenyl propyl ether.196... 

A technique that has proved to possess considerable usefulness in epoxide synthesis is addition of diazoalkanes. particularly of the parent eubatanoe djazomethane, to suitable carbonyl groups. 

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