Diazoalkanes reaction with

Two types of products are generally obtained by reaction of ketones with diazoalkanes a homologous carbonyl compound and a small amount of oxirane. The reaction scheme is presented in Eq. 85. 

Addition of the diazoalkane nucleophile is followed by an reaction with ring-closure or a homologous ketone is formed with a 1,2-alkyl rearrangement (shift). Spirooxiranes are produced from cyclic ketone derivatives with diazomethane (Eq. 86).  

Which homologous diazoalkanes, a mixture of cycloheptanones and spirooxiranes results. In cyclic ketones equatorial attack is usually favored.  

A perfluoro-enol also reacts with diazoalkanes (Eq. 87).  

The reaction of a diazoalkane with an ester carbonyl group has been reported (Eq. 88). It was found that the reaction is promoted by the presence of a nitro group in the Q -position. ° 

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As noted in the preceding section, one of the most general methods of synthesis of esters is by reaction of alcohols with an acyl chloride or other activated carboxylic acid derivative. Section 3.2.5 dealt with two other important methods, namely, reactions with diazoalkanes and reactions of carboxylate salts with alkyl halides or sulfonate esters. There is also the acid-catalyzed reaction of carboxylic acids with alcohols, which is called the Fischer esterification. 

Muller has explored enantioselective C-H insertion using optically active rhodium complexes, NsN=IPh as the oxidant, and indane 7 as a test substrate (Scheme 17.8) [35]. Chiral rhodium catalysts have been described by several groups and enjoy extensive application for asymmetric reactions with diazoalkanes ]46—48]. In C-H amination experiments, Pirrung s binaphthyl phosphate-derived rhodium system was found to afford the highest enantiomeric excess (31%) of the product sulfonamide 8 (20equiv indane 7, 71% yield). 

In the light-induced reactions with diazoalkanes, methylene, the photolytic fragment from diazomethane, may be interposed between the halogen atom in the organic halide and the carbon atom to which it is attached,289 290 or may add to the double bonds in the aromatic ring.58 69... 

One other type of esterification process which formally involves the carboxylic acid is the Reaction with diazoalkanes. Diazomethane in particular is widely used for the synthesis of methyl esters, viz. 

Access to alkyl substituted derivatives of the homotropylidene complexes is provided via the >j4-tropone iron complex by reaction with diazoalkanes, followed by mild thermolysis of the 3+2 py razoline adduct to give the corresponding homotropone complexes (equation 149)217,218. The 8,8-dimethyl derivative was used as starting material for the preparation of the fluxional ( 5-2,8,8-trimethylbicyclo[5.1.0]octa-2,4-dienylium)Fe(CO)3 cation complex219. More recently (homotropone)Fe(CO)3 was used for the synthesis of unique chiral 1,2-homoheptafulvene iron complexes220 221. 

Vinyl sulfoxides have been used as synthetic equivalents of alkynes in reactions with diazoalkanes to prepare pyrazoles. The initially obtained adducts subsequently eliminate or rearrange the sulfoxide moiety to achieve pyrazoles lacking the sulfur function. Thus, the adducts resulting by reaction of CH2N2 with the sulfinylated double bond of allenyl sulfoxides 213 are transformed through a sulfoxide-sulfenate rearrangement into hydroxymethyl pyrazoles 214 [168], whereas those obtained by reaction with sulfinyl coumarins 215 suffered sulfinyl elimination into the pyrazoles 216 [169]. In both cases l,H-pyrazoles were obtained as a consequence of a final tautomerization step (Scheme 101). These studies were carried out on racemic sulfoxides. 

In certain cases l,2-dinitro-2-phenylethene also forms the corresponding nitro-pyrazoles in reaction with diazoalkanes [492 194] (Scheme 69). 

Substituted 1,4-diazooxides rect with secondary aliphatic amine to give the corresfxjnding triazene (diazoamino compounds) in high yield, while the products with primary amine are surprisingly unstable and deompose by a radical mechanism. Reactions with diazoalkanes yield asymmetrical azine 29 (15) in the case of 1,4-diazooxide, and cyclic benzoxadiazines 30 with 1,2-diazooxides (16) . 

An alternative procedure involves in situ generation of sulfenes from sulfonyl chlorides and subsequent reaction with diazoalkanes affording a mixture of cis- and tram-thiirane 1,1-dioxides 2 and 3116. 

The increase in protonation sites in the oxopurines with increasing oxygen functions extends the possibilities for Ai"-alkylation sites. Normally in the case of monooxo- and dioxo-purines, with the exception of reactions with diazoalkanes, many of which are probably free radical in nature, alkylating agents even in alkaline solutions produce only Af-alkyl derivatives. Trioxopurines such as uric acid derivatives are an exception. The nature of the alkylation and the site(s) of attack nevertheless still vary according to the solvent, pH and temperature. 

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