Reduction of diazo compound

Non-functionalized aliphatic diazo compounds are fairly rare, and so are their reductions. Good examples of the reduction of diazo compounds to either amines or hydrazones are found with a-diazo ketones and a-diazo esters (pp. 124, 125, 160). 

The reduction of diazo compounds to the hydrocarbon may be accomplished by means of stannous chloride, sodium stannite or under certain conditions alcohols act as a reducing agent being themselves thereby oxidized to aldehydes. 

Fischer phenylhydrazine synthesis. Formation of arylhydrazines by reduction of diazo compounds with excess sodium sulfite and hydrolysis of the substituted hydrazine sulfonic acid salt with hydrochloric acid. The process is a standard industrial method for production of arylhydrazines. 

The majority of preparative methods which have been used for obtaining cyclopropane derivatives involve carbene addition to an olefmic bond, if acetylenes are used in the reaction, cyclopropenes are obtained. Heteroatom-substituted or vinyl cydopropanes come from alkenyl bromides or enol acetates (A. de Meijere, 1979 E. J. Corey, 1975 B E. Wenkert, 1970 A). The carbenes needed for cyclopropane syntheses can be obtained in situ by a-elimination of hydrogen halides with strong bases (R. Kdstcr, 1971 E.J. Corey, 1975 B), by copper catalyzed decomposition of diazo compounds (E. Wenkert, 1970 A S.D. Burke, 1979 N.J. Turro, 1966), or by reductive elimination of iodine from gem-diiodides (J. Nishimura, 1969 D. Wen-disch, 1971 J.M. Denis, 1972 H.E. Simmons, 1973 C. Girard, 1974),... 

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],... 

Based on his previous work on the catalytic double addition of diazo compounds to alkynes173 using Cp RuCl(COD),174 Dixneuf has developed an efficient one-step synthesis of alkenyl bicyclo[3.1.0]-hexane derivatives of type 163 from enyne precursors 162 (Scheme 43). The catalytic cycle starts with the formation of an Ru=CHR species. It then adds to an alkyne to form ruthenacyclobutene 166, which evolves into vinylcarbene 167. [2 + 2]-Cycloaddition of 167 gives ruthenacyclobutane 168. The novelty in this transformation is the subsequent reductive elimination to give 170 without leading to the formation of diene 169. This can be attributed to the steric hindrance of the CsMes-Ru group. 

It should be noted, however, that the 1,3-dipolar cycloaddition chemistry of diazo compounds has been used much less frequently for the synthesis of natural products than that of other 1,3-dipoles. On the other hand, several recent syntheses of complex molecules using diazo substrates have utilized asymmetric induction in the cycloaddition step coupled with some known diazo transformation, such as the photochemical ring contraction of A -pyrazolines into cyclopropanes. This latter process often occurs with high retention of stereochemistry. Another useful transformation involves the conversion of A -pyrazolines into 1,3-diamines by reductive ring-opening. These and other results show that the 1,3-dipolar cycloaddition chemistry of diazo compounds can be extremely useful for stereoselective target-oriented syntheses and presumably we will see more applications of this type in the near future. 

The mixture of 5 and 6 can be converted to 9 by reduction, separation and then epimerization/reduction of one isomer. Alcohol 9 is then further subjected to similar procedure as for 1 to give tricyclic ether 12, through the same Cu(tfacac)2-catalyzed ylide formation/[2,3]-sigmatropic rearrangement of diazo compound 10 (Scheme 2). 

Such a reaction agrees perfectly with the new formula which has been generally accepted as expressing the constitution of the free diazo base and the salts. The base thus takes the name benzene diazonium hydroxide and the salts, e.g., the chloride, benzene diazonium chloride signifying their ammonium character. The new formula does not, however, fit the reactions by which diazo. compounds are converted into azo or amino azo compounds nor the reduction of diazo benzene to phenyl hydrazine. Thus we have two formulas neither of which... 

The bromination of sinomenine gives 1-bromosinomenine [5, 9, 21] [xn], the structure of which is revealed by the reduction of the compound to 1-bromodihydrosinomenine, dihydrosinomenine, and sinomenine, and by the fact that the diazo-reaction with 1-bromosinomenine is much less intense than with sinomenine [21]. A second substance is also produced by the bromination of sinomenine, but this is non-phenolic and is discussed later under 1-bromosinomeneine. 

Pretreatment procedures included reduction on Cd-column, reduction by hydrazine addition with copper catalyst, or addition of NH4CI buffer. The final determination was performed by e.g. SPEC of diazo-compound at 540 nm or 1C (conductivity). A detailed description of the techniques is given in the certification report [4]. 

There are several aspects of electron transfer reactions to and from diazo compounds First, the processes in an electrochemical cell, in particular those taking place at the surfaces of the cathode and the anode second, the structure of the intermediates and final products obtained in electrochemical processes third, reactions of diazo compounds carried out with inorganic and organic reduction or oxidation reagents. 

In this section, we discussed radicals generated by one-electron transfer to or from diazo compounds, i. e., redox reactions. We will add here a reaction of diazo compounds with stable organic n cation radicals, although this process is neither a reduction nor an oxidation. 

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