By the Bamford-Stevens

A non-Kekule molecule, a /n-xylylene (88), has been generated by the Bamford-Stevens reaction of a fulvene-ketene adduct (85), via the homofulvene (87) from the intermediate carbene (86). This unstable intermediate readily dimerizes to octamethyl[2.2]metacyclophane (89 Scheme 9). ... 

Chen s stereospecific total synthesis of cycloeudesmol 48 started with the hydrazone 46, which was converted to the allylic alcohol 47 by the Bamford-Stevens reaction followed by DMF trapping of the vinyl anion and sodium borohydride reduction. This allylic alcohol 47 was then taken on through a further ten steps to yield the natural product cycloeudesmol 48. 

X = NO2) with triethyl phosphite or by heating the azide (229 X = N3) was not successful, but phenothiazine analogues were obtained by the Bamford-Stevens reaction with (229 X = CH=NNHTos). ... 

Okfm Syntheses. Conversion of aldehydes and ketones to olefins by the base-catalyzed decomposition of -toluenesulfonic (Ts) acid hydrazones (10) is known as the Bamford-Stevens reaction (54,55). 

The Bamford-Stevens decomposition of tosylhydrazones by base has been applied to steroids, although not extensively. It has been demonstrated that the reaction proceeds via a diazo compound which undergoes rapid decomposition. The course of this decomposition depends upon the conditions in proton-donating solvents the reaction has the characteristics of a process involving carbonium ions, and olefins are formed, often accompanied by Wagner-Meerwein-type rearrangement. In aprotic solvents the diazo compound appears to give carbene intermediates which form olefins and insertion products ... 

A more promising procedure for the formation of alkenes from tosylhydrazones is represented by the Shapiro reaction It differs from the Bamford-Stevens reaction by the use of an organolithium compound (e.g. methyl lithium) as a strongly basic reagent ... 

The l,3-dithian-2-ylidene substituted carbene (54), accessible from the tosylhydrazone (53) by a Bamford - Stevens reaction, not only participates in cycloaddition reactions but is also a source of 4,8-dithiaspiro[2.5]oct-l-ene 6JCS(P1)2773>. 

Compound 34 can be synthesized by a Bamford-Stevens procedure from compound 33. Loer explored the cyclization of 32 with polyphosphoric acid (PPA), followed by decomposition of the tosylhydrazone to form the desired 177-2,1-benzothiazine 2,2-dioxide 34 in good overall yield (Scheme 8) <66JOC3531>. 

The intermediate bicyclo[2,2,l]heptyl cation has been written in Fig. 1 in its unbridged form by analogy with conclusions reached from studies of the Bamford-Stevens reaction of 18 stereospecifically deuteriated in either the 6-exo- or 6-endo positions (Nickon and Werstiuk, 1966). Under aprotic conditions (diglyme/sodium methoxide), the product is entirely norticyclene (19), formed without loss of deuterium in keeping with carbene formation followed by intramolecular insertion. Under standard protic conditions, 19 still constitutes more than 90% of the reaction product, but 19% of the label is lost from ea o-deuteriated starting material and 52% from the endo-deuteriated compound,... 

The reduction of a carbonyl group to an olefin has been accomplished by the Shapiro modification5 of the Bamford-Stevens reaction and by the hydride reduction of the corresponding enol ether,6 enol acetate,7 or en-amine.8 The nickel reduction of the thioketal has also been used successfully.9... 

The parent 3-piperideine (3) was prepared from l-acetyl-4-piperi-done by conversion into the p-toluenesulfonylhydrazone and thermal fission of the latter in alkaline media (the Bamford-Stevens reac-... 

Mechanism The first step of the Bamford-Stevens reaction is the formation of the diazo compound A by the treatment of tosylhydrazone with a base. The reaction mechanism involves a carbene B in an aprotic solvent (Path A) and carbocation C in a protic solvent (Path B) (Scheme 4.53). When an aprotic solvent is used, predominantly Z-alkenes are obtained, while a protic solvent gives a mixture of E- and Z-alkenes. If there is a choice of product, the more substituted alkene is produced predominantly. 

Treatment of a,p-unsaturated tosylhydrazones with NaBH4 in MeOH affords principally allylic ethers from cyclic derivatives and pyrazoles with most noncyclic examples. This divergent behavior compared to saturated tosylhydrazones has been attributedto a lessening of the electrophilicity of conjugated imine ir-bonds, which allows initial abstraction of the acidic N—H proton by BH4 to compete with reduction, and gives alternative reactions related to the Bamford-Stevens process as depicted in Scheme 4. An exception to this may be the deoxygenation of conjugated vinyl triflates (entry 11, Table 6). The cyclopropanation and elimination products produced in entry 4, Table 6 also probably arise from similar, alternative reaction paths. ... 

Solid-state photolyses were conducted in argon-purged borosilicate flasks. After 2 h, no more diazirine 26 was present by NMR nor by gas chromatographic (GC) analysis. The results of solution photolyses of diazirine 26 are shown in Table 3. Carbene 27 can also be generated from the 2-methylcyclohexanone p-tosyl hydra-zone sodium salt (33) via the Bamford-Stevens reaction.116 The gas phase results are also included in Table 3 as are the results of Wilt and Wagner.111... 

Solvolysis can also occur from the diazonium salts derived from the intermediate diazocy-clopropanes. Ring opening of cyclopropyldiazonium salts accounts for the solvolysis products in Table 2, entries 8 and 9. Evidence for this is seen when sodium methoxide is replaced by the weaker base, sodium hydrogen carbonate, in which case only the methyl ethers derived from methanolysis were obtained. The a-elimination reaction of 1-cyclopropyl-1-nitrosourea with base likely involves diazocyclopropanes as intermediates which readily eliminate molecular nitrogen to form cyclopropylidenes. A more direct approach to diazocyclopropanes involves the Bamford-Stevens route via tosylhydrazones. Thus di-/er/-butylallene (19) was prepared from the tosylhydrazone of ( )-2,3-di-tert-butylcyclopropanone on treatment with base. ... 

Loev and co-workers152 prepared the unsubstituted lH-2,l-benzothia-zine 2,2-dioxide (239) by the route of Scheme 11. Methyl chlorosulfonyl-acetate was converted into the sulfonanilide (235) by reaction with aniline. Hydrolysis of the ester group in 235 gave 236 which, with polyphosphoric acid, cyclized to 1 H-2,l-benzothiazin-4-one (237). Spectral data indicated that 237 existed in the keto form. Ketone 237 was converted to the tosylhydra-zone 238 which, by a Bamford-Stevens reaction, afforded 239 in good overall yield. The iV-methyl analog of 239 was also prepared by the above reaction sequence using N-methylaniline. 

The first successful syntheses of phosphorus-containing diazoalkyl compounds (1) appear to have been reported independently by two groups of workers. Petzold and Henning employed a method presently described as that of diazo transfer, in which an active methylene compound, as its anion, is treated with an aromatic sulphonyl azide. Seyferth et al on the other hand, reported on a development to the Bamford-Stevens reaction, in which a carbonyl/7-toluenesulphonylhydrazone is treated with a base. Both methods thus depend on modifications to compounds with existing phosphorus-carbon bonds, as do other procedures which have since been developed. 

The Bamford-Stevens synthesis is related to the Shapiro reaction (Shapiro and Heath, 1967 reviews Shapiro, 1976 Adlington and Barrett, 1983), in which a 4-toluenesulfonyl hydrazone of an aldehyde or a ketone is treated with at least two equivalents of a very strong base, usually, methyllithium (see Organic Syntheses examples of Chamberlin et al., 1983, and Shapiro et al., 1988). The Shapiro reaction leads to an olefin by a hydrogen shift. The mechanism has been proposed by Casanova and Waegell (1975) as given in (2-34). This mechanism involves a diazenide anion 2.81 as intermediate. 

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