Insertion diazomethane

The diazomethane insertion into ketones and aldehydes to provide their homologs also involves migration of an alkyl group to an electron-deficient carbon center of a zwitterion through a pentacoordinate carbocation according to the mechanism depicted in Equation (6.29). 

There are few examples of this variation in the literature. The variation relies on the alkylation of thiolactams (in replacement of cyclohexanones) by the Michael addition of diazomethyl vinyl ketone (in replacement of methyl vinyl ketones) followed by ring closure using rhodium(II) acetate mediated diazomethane insertion. The diazomethyl entity can also be added after the Michael addition step. The reaction affords six-membered rings with... 

A versatile oxirane synthesis via (64) is the sulfur ylide approach (B-75MI50504, cf. 76TL457), which in effect inserts a CR2 group into a carbonyl group (Scheme 71). Older, less generally useful versions of this insertion utilize diazomethane or dibromomethane-butyllithium. 

A valuable extension of the diazomethane reaction for the preparation of A-homosteroids was discovered by Johnson, Neeman and Birkeland " who found that a,j5-unsaturated ketones are homologated by reaction with diazomethane in the presence of either fluoroboric acid or boron trifluoride. The main product is formed by the insertion of a methylene group between the carbonyl group and the unsaturated a-carbon to give a / ,y-unsaturated ketone. 

The well-known reaction leading to ring expansion of cyclic ketones has been applied to derivatives of oxo sugars in an attempt to develop a new route to novel deoxy sugars. By treatment with diazomethane both a five-membered (42) and a six-membered (26) sugar ring have been expanded by insertion of a methylene group. 

Owing to the high reactivity of the intermediates involved, intermolecular carbene insertion reactions are not very selective. The distribution of products from the photolysis of diazomethane in heptane, for example, is almost exactly that expected on a statistical basis.211... 

The nature of the photochemically produced methylene has been the subject of considerable study. Evidence tends to indicate that this species is produced in its singlet state photochemically. Photolysis of diazomethane in the gas phase or in solution in the presence of excess cis- or trans-2-butene produces cyclopropane products due to methylene insertion in which the... 

The carbene moieties of methyl diazoacetate 353), dimethyl diazomalonate 3S3) and diazomethane 3541 have been inserted into the Se—Se bond of diaryl diselenides. 

The Lewis acid-Lewis base interaction outlined in Scheme 43 also explains the formation of alkylrhodium complexes 414 from iodorhodium(III) meso-tetraphenyl-porphyrin 409 and various diazo compounds (Scheme 42)398), It seems reasonable to assume that intermediates 418 or 419 (corresponding to 415 and 417 in Scheme 43) are trapped by an added nucleophile in the reaction with ethyl diazoacetate, and that similar intermediates, by proton loss, give rise to vinylrhodium complexes from ethyl 2-diazopropionate or dimethyl diazosuccinate. As the rhodium porphyrin 409 is also an efficient catalyst for cyclopropanation of olefins with ethyl diazoacetate 87,1°°), stj bene formation from aryl diazomethanes 358 and carbene insertion into aliphatic C—H bonds 287, intermediates 418 or 419 are likely to be part of the mechanistic scheme of these reactions, too. 

Hydride 38 is converted to the methyl derivative 40 upon treatment with diazomethane in the presence of Cu (equation 8)21. Presumably this insertion reaction proceeds with retention of configuration. 

An interesting report has been made of methylene insertion into the P-C linkage of a-(acyloxy)iminoalkylphosphonates derived from carbohydrates.181 This reaction system, using diazomethane, allows extension of the chain by a single carbon atom, with that atom (methylene group) attached directly to the phosphorus. 

Insertion into Si—I bond.1 Reaction of trimethylsilyl iodide or triflate with diazomethane results in insertion of a methylene group into the Si—I or Si—OTf bond (equation I). Similar insertion into (CH3)3SiBr requires ZnBr2 catalysis. 

Elimination of trimethylchlorosilane and nitrogen occurs when the (phos-phino)(silyl)diazomethane la is reacted with para-toluenesulfinyl chloride at low temperature. The formation of the four-membered heterocycle 92, obtained in 87% yield, can be rationalized by a multiple-step mechanism involving the formation of the (phosphino)(sulfinyl)carbene 2v. The insertion of the (phosphoryl)(sulfenyl)carbene 91, resulting from a 1,3-oxygen shift from sulfur to phosphorus in 2v, into a carbon-hydrogen bond of a diisopropylamino group readily accounts for the formation of 92.84... 

The insertion products obtained by the photolysis of diazomethane in the gas phase in the presence of alkanes also include products originating from ethyl radicals, the formation of which must be explained by postulating vibrationally excited species The relative rates of abstraction of CH2 from alkanes are... 

Evident cases of abstraction/recombination mechanism are observed with phenylsubstituted carbenes. Diphenyl-diazomethane, which is photolyzed to give the triplet diphenyl-carbene, very readily abstracts a hydrogen atom from the benzyl group of toluene. The primarily formed radicals can now recombine to give a formal "insertion product — 1,1,2-triphenylethane — or they can recombine to form 1,1,2,2-tetraphenylethane and 1,2-diphenylethane... 

Photolysis of diazomethane in the gas phase produces CH2 which can add to cis-2-butene to form dimethyl-cyclopropanes 32 and 33. The insertion products 34 and 35 are also formed... 

This technique has been repeatedly utilized. Photolysis of diazomethane in the liquid phase yields methylene in the singlet state, as is shown by the practically stereospecific addition to cis- or trans-butene. Dilution with perfiuoropropane reduces the degree of stereospecifity as well as the amount of C—H-insertion, indicating that triplet methylene is involved A similar effect has been reported for CF3CH which, on dilution with perfluoro-diethylether (in the gas phase), adds in a non-stereospecific manner owing to the presence of the triplet... 

Ylides other than acceptor-substituted diazomethanes have only occasionally been used as carbene-complex precursors. lodonium ylides (PhI=CZ Z ) [1017,1050-1056], sulfonium ylides [673], sulfoxonium ylides [1057] and thiophenium ylides [1058,1059] react with electrophilic transition metal complexes to yield intermediates capable of undergoing C-H or N-H insertions and olefin cyclopropanations. 

Aluminum porphyrins first came to attention with the discovery that the simple alkyl complex Al(TPP)Et was capable of activating CO2 under atmospheric pressure. Both irradiation with visible light and addition of 1-methylimidazole were required for the reaction, which was proposed to proceed by initial coordination of the base to aluminum. The aluminum porphyrin containing direct product of CO2 insertion was not isolated, but was proposed on the basis of IR data to be (TPP)A10C(0)Et, which was then treated with HCl gas, presumably liberating propanoic acid, subsequently isolated as the butyl or methyl ester after reaction with 1-butanol or diazomethane, respectively [Eq. (5)]. Insertion of CO2 into the Al—C bond of an ethylaluminum phthalocyanine complex has also been reported. ... 

The addition of different types of carbenes onto bicyclopropylidene (1) is a common method for the preparation of [3]triangulane derivatives as well as branched trianguianes and normally proceeds without complications (for a review see [77]). Thus, the cyclopropanation under Gaspar-Roth [60] or modified Simmons-Smith [111] conditions gave dispiro[2.0.2.1]heptane ([3]triangulane, 97) in 80 [105] and 15% yield [5], respectively (Scheme 23). The palladium(II) acetate-catalyzed cycloprop anation of 1 with diazomethane, however, gave a number of products resulting from insertion of one or more than one methylene units into an initially formed palladacyclobutane 115 [112,113] (Scheme 23). 

---