Diazomethane, decomposition

When subjected to the Conia modification of the Simmons-Smith reaction or cuprous chloride-catalyzed diazomethane decomposition, triquinacene was converted to two monocyclopropanated, two doubly cyclopropanated, and two triply cyclo-propanated products.403) Subsequent photochlorination of 454 with r-butyl hypochlorite at —50 °C has been shown to proceed with ring expansion and formation of 455.404) In contrast, //-exo-trishomotriquinacene (456) could be converted to trichloride 457 with retention of the hexacyclic carbon framework 04)... 

The monophosphine complexes Os3(/u-H)2(CO)9L react with diazomethane to give N2 and a wide range of homologous alkenes. The rates of diazomethane decomposition correlate well with the electronic nature of L rather than its size, with less donating ligands showing higher rates. 

A paper by Sailor and Hogan [2] provides a very detailed siunmary on the history of polyolefins which includes research reported from 1897-1940 in which linear polyethylene was prepared by various scientists without directly polymerizing ethylene. This early research clearly demonstrated that a linear polymethylene was prepared with a relatively high molecular weight as indicated by a crystalline melting point of 132-134 C. For example, linear polymethylene was prepared by diazomethane decomposition and by hydrogenation of carbon monoxide over ruthenium and cobalt catalysts. 

A classic shock-tube study concerned the high-temperature recombination rate and equilibrium for methyl radical recombination [M, Ml- Methyl radicals were first produced in a fast decomposition of diazomethane at high temperatures (T > 1000 K)... 

The diazomethane-ether solution should be dry. If in doubt, it may be dried with A.R. potassium hydroxide pellets. The anhydrous ethereal solution may be stored in a smooth glass flask or bottle in a refrigerator for a week or so since slow decomposition occurs with hberation of gas, the containing vessel should be protected by a calcium chloride (or cotton wool) guard tube. 

During the reaction the alumina usually attains a pink color which is due to some decomposition of p-tolylsulfonyldiazomethane. However, the colored decomposition products adhere strongly to the alumina and will therefore not contaminate the final product. If the alumina becomes reddish rather than pink, the type of the alumina in use may be too basic, causing more extensive decomposition of the -tolylsulfonyl-diazomethane the reaction time should then be reduced as much as possible to prevent a considerable decrease in yield. 

Aminocyclopropanes were prepared from enamines by the addition of Simmons-Smith reagent (688) or best through the cuprous-chloride-promoted decomposition of diazomethane (689). The reaction of an enamine with chloroform and base and opening of the resultant aminocyclopropane to an ynamine was reported (690). 

In this review an attempt is made to discuss all the important interactions of highly reactive divalent carbon derivatives (carbenes, methylenes) and heterocyclic compounds and the accompanying molecular rearrangements. The most widely studied reactions have been those of dihalocarbenes, particularly dichlorocarbene, and the a-ketocarbenes obtained by photolytic or copper-catalyzed decomposition of diazo compounds such as diazoacetic ester or diazoacetone. The reactions of diazomethane with heterocyclic compounds have already been reviewed in this series. ... 

When diazomethane is slowly added to excess lactam, the anions formed can interact with unreacted lactam by means of hydrogen bonds to form ion pairs similar to those formed by acetic acid-tri-ethylamine mixtures in nonpolar solvents. The methyldiazonium ion is then involved in an ion association wdth the mono-anion of a dimeric lactam which is naturally less reactive than a free lactam anion. The velocity of the Sn2 reaction, Eq. (7), is thus decreased. However, the decomposition velocity of the methyldiazonium ion, Eq. (6a), is constant and, hence, the S l character of the reaction is increased which favors 0-methylation. It is possible that this effect is also involved in kinetic dependence investigations have shown that with higher saccharin concentrations more 0-methylsaccharin is formed. 

The results of this type of experiment show that CH2 itself is usually formed as a singlet species, that can decay to the triplet state, which consequently has a lower energy (MO calculations and experimental determinations show that the difference in energy between singlet and triplet CH2 is 8-10kcal mol or 33-42 kJ moP ). However, it is possible to prepare triplet CH2 directly by a photosensitized decomposition of diazomethane.Methylene (CH2) is so reactive " that it generally reacts as the singlet before it has a chance to decay to the triplet state. 

In studies on l-diazo-2-ketosulfones, Shioiri et at. found that the thermal decomposition of benzoyl(sulfonyl)diazomethanes 6 with benzyl alcohol in acetonitrile also gave two products.<82CPB526> One is the 4-sulfonyloxazole 7 whereas the other product 8 results from rearrangement and reaction with the alcohol. The ratio of products varies with the nature of the sulfone substituent with the benzyl group giving highest yields of oxazole (Scheme 5). 

Carbenes from Diazo Compounds. Decomposition of diazo compounds to form carbenes is a quite general reaction that is applicable to diazomethane and other diazoalkanes, diazoalkenes, and diazo compounds with aryl and acyl substituents. The main restrictions on this method are the limitations on synthesis and limited stability of the diazo compounds. The smaller diazoalkanes are toxic and potentially explosive, and they are usually prepared immediately before use. The most general synthetic routes involve base-catalyzed decomposition of V-nitroso derivatives of amides, ureas, or sulfonamides, as illustrated by several reactions used for the preparation of diazomethane. 

Similarly, the direct [Eq. (11.24)] and photosensitized [Eq. (11.25)] decomposition of diazomethane in the presence of cyclohexene yielded product distributions indicative of greater selectivity in the triplet methylene addition ... 

Some examples of carbene dimer formation resulting from diazoalkane decomposition on transition-metal surfaces have been reported. Diazomethane is decomposed to give ethylene and N2 upon passage over a C0O/M0O3 catalyst as well as on Ni, Pd, Fe, Co, Ru and Cu surfaces 367). Similarly, 2-diazopropane is readily decomposed on Raney nickel 368). At room temperature, propene and N2 were the only detectable products, but above 50 °C, the carbene dimer 2,3-dimethyl-2-butene started to appear which reached its maximum yield at 100 °C, where approximately 40 % of the carbene fragments dimerized. It is assumed 367,368), that surface carbenes are formed as intermediates from both diazomethane and 2-diazopropane which either dimerize or desorb by migration of a P-hydrogren, if available (Scheme 40). 

CuS04-catalyzed decomposition of the (l-sila-cyclopentadienyl)diazomethane 398 did not furnish defined products. The desired rearrangement reactions to a silabenzene and a l-ethylidene-l-sila-2,4-cyclopentadiene, both trapped by /-butanol, were brought about by irradiation of 398, however 388... 

Methylene ( CH2), the simplest carbene, can be prepared by the decomposition of diazomethane (CH2N2). 

In a study aimed at elucidating the mechanism of the thermal decomposition of spiropentane 229, the two regioisomeric pyrazolines 227 and 228 were obtained in high yield by allowing a solution of MCP (1) and diazomethane (226) (or diazomethane-d2) in diethylether to stand at 3 °C for three weeks (Scheme 37) [59]. 

As follows from the comparison of the rates of oxidation and destruction of linear and branched polyalkenes, the branched form possesses more susceptible tertiary C—H bonds and oxidizes more rapidly (but degrade more slowly) than the linear form. This was observed for PS, PE, PP, polyfrt-isopropyl styrene), polymethylene, and polymers produced by the decomposition of diazomethane-diazoethane and diazomethane-diazobutane mixtures [125], The number of cleavages per oxygen molecule consumed at 403 K amounts to 0.25 for PE and to 0.04 for PP. 

Diazomethane when heated with copper powder gives nitrogen and an insoluble polymethylene, indicating that one of its reactions is the decomposition into methylene radicals. The methylene radical can also be formed in the gas phase and detected by a mirror experiment.81 The pyrolysis of ketene in the gas phase gives carbon monoxide and methylene radical. The methylene radical both reacts with itself to give ethylene and removes tellurium mirrors, forming tellurform-aldehyde.82 Thus the methylene diradical(P) behaves as expected. 

Photochemical decomposition of diazomethane yields methylene, which reacts with benzene to form toluene and cycloheptatriene (via norcaradiene) (Scheme 5).65 66... 

Diazomethane is one of the most versatile and useful reagents in organic chemistry in spite of the fact that it is very highly toxic and dangerously explosive and can not be stored without decomposition. 

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