Tosylhydrazone Bamford-Stevens reaction

Sodium methoxide Pyrazolo[l,5-a]pyridines from homo-p-quinone bis(tosylhydrazones) Bamford-Stevens reaction... 

Ethylene derivatives from tosylhydrazones Bamford-Stevens reaction... 

The alkyl lithium method gives high yields of -olefins from 17-ketones via the tosylhydrazones. A -Olefins are formed from 6- and 7-ketones. (Compare with the Bamford-Stevens reaction which gives A - and A -olefins, respectively.) In the presence of an excess of alkyl lithium, alkylation may occur. 

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 ... 

An unusual synthesis of the l,6-dihydro-l,2,3-triazine system 8 involves the Bamford-Stevens reaction of cis-aziridinylketone tosylhydrazones 7 in the presence of a "slight excess" of sodium hydride or sodium ethoxide. If a large excess of sodium ethoxide is used then isopropylamino-3,5-diaiylpyrazoles are formed <%H(43)1759>. 

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>. 

Cycloadditions to [6,6]-double bonds of Cjq are among the most important reactions in fullerene chemistry. For a second attack to a [6,6]-bond of a C q monoadduct nine different sites are available (Figure 10.1). For bisadducts with different but symmetrical addends nine regioisomeric bisadducts are, in principle, possible. If only one type of symmetrical addends is allowed, eight different regioisomers can be considered, since attack to both e - and e"-positions leads to the same product. Two successive cycloadditions mostly represent the fundamental case and form the basis for the regioselectivity of multiple additions. In a comprehensive study of bisadduct formations with two identical as well as with two different addends, nucleophilic cyclopropanations, Bamford-Stevens reactions with dimethoxybenzo-phenone-tosylhydrazone and nitrene additions have been analyzed in detail (Scheme 10.1) [3, 9, 10]. 

Phenyldiazomethane, 1, 834. A new method for preparation of this (and other aryl-diazomethanes) involves a vacuum pyrolysis of the sodium salt of benzaldehyde tosylhydrazone, a method introduced for carrying out the Bamford-Stevens reaction. The yield is 80%, the highest yield yet reported. Another advantage is that the reagent is obtained free from solvents. The pyrolysis can also be coitducted in ethylene glycol at 80° with extraction of the aryldiazomethane into hexane.1 Caution All diazo compounds arc highly toxic and potentially explosive. 

Bamford-Stevens reaction of the tosylhydrazones of the readily available tetrahydrofuran-3-ones provides a useful synthesis of 2,3-dihydrofurans which may be dehydrogenated to furans with 2,3-dichloro-5,6-dicyano-l,4-benzoquinone (66CJC1083). Tetrahydrofuran-2-ones (y-butyrolactones) may be alkylated in the 3-position with LDA and an alkyl halide. The products on reaction with phenyl selenylchloride and LDA, and subsequent oxidation, yield 3-alkylfuran-2(5//)-ones reducible with DIBAL to furans (75JOC542). 

Bamford-Stevens Reaction- initial conversion of a tosylhydrazone to a diazo intermediate... 

The Shapiro Reaction, a variation on the Bamford-Stevens Reaction, is the base-induced reaction of tosylhydrazones to afford alkenes. This reaction is carried out with two equivalents of an organolithium compound. 

Some 2-deoxy-analogues of rubrosterone have been reported.73 The synthesis commenced with a Bamford-Stevens reaction upon 3/3,17/3-diacetoxyandrost-5-en-7-one tosylhydrazone to yield the corresponding 5,7-diene. Successive chromic acid and selenium dioxide oxidation of this diene furnished the 2-deoxyrubrosterones (177 R1 = OAc, R2 = H, R3 = OH, X= 17/3-0Ac,H 5a-H) and (177 R = OAc, R2 = R3 = H, X = 17/3-OAc,H 5a-H) respectively. Alkaline hydrolysis of the latter derivative afforded an A-homo-B-nor-steroid (178). The rubrosterone (177 R1 = R2 = R3 = OH, X = O 5/3-H), which possesses antidiabetic activity, has been prepared by oxidative degradation of the cholestene (179), itself obtained from ecdy-sterone.74... 

The Bamford-Stevens reaction is a tosylhydrazones, 4.106, decomposition with a base to form alkenes. 

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. 

Interesting stereochemical aspects of the protic Bamford-Stevens reactions of the epimeric 7-oxohexa-hydrocannabinol tosylhydrazone acetates (70) and (72) have been recently demonstrated. When the axial epimer (70) was added to sodium ethylene glycol, the ring expansion product (71) was obtained in 38% yield. On the other hand, reaction of the equatorial epimer (72) under the same conditions yielded (73) in 56% yield (equations 45 and 46). Notably, the aprotic Bamford-Stevens reaction of the axial epimer (70) gave rise to (73) (30-40% yield) after acetylation. 

A structurally intriguing dimethyl[6]ditriaxane (84) has been synthesized from the polycyclic diketone tosylhydrazone (83) by the aprotic Bamford-Stevens reaction via a carbenic interm iate (equation 49). ... 

The Bamford-Stevens reaction is the key step in a convenient procedure for the conversion of aldehydes and ketones into the corresponding diazoalkanes. Here, the use of 2,4,6-triisopropylbenzenesulfo-nylhydrazone (trisylhydrazone) is far superior to the use of the more common tosylhydrazones (equation 50). This behavior is attributed to the greater release of steric compression in the decomposition of ort/io-substituted arenesulfonylhydrazones. 

Mechanistic information on the photolytic Bamford-Stevens reaction is provided by the successful isolation of a diazo hydrocarbon as a reaction intermediate from the direct photolysis of a tosylhydrazone sodium salt (90 Scheme 10). This study also clarifies that the carbene derived thermally and that derived photolytically behave differently with respect to the stereoselectivity of the 1,2-hydrogen shift that produces the alkene. 

The Bamford-Stevens reaction is particularly effective for the generation of 9-phenyl-l(9)-homo-cubene (93), the most twisted alkene yet known. Thus, thermolysis of the cubyl phenyl ketone tosylhydrazone (91) in ethanolic sodium ethoxide or photolysis of the diazo compound (92) in ethanol both give good conversions to a 3 2 mixture of the isomeric ethers (95) and (96) (Scheme 11). The formation of (96) suggests the intervention of l-phenyl-9-homocubylidene (94) via the rearrangement of (93). 

As already demonstrated in the Bamford-Stevens reaction, 2,4,6-triisopropylhydrazones (trisylhydra-zones) are also found to undergo fragmentation more easily than the corresponding tosylhydrazones in... 

The reaction of tosylhydrazones with sodium in ethylene glycol to give alkenes had been observed before (Bamford-Stevens reaction) other bases, e.g. NaOMe, alkali metal hydrides and NaNH2 were also used. However, in these cases side reactions occur and, in contrast to the Shapiro reaction, the more highly substituted alkene is predominantly formed. Two mechanisms are discussed for these reactions a mechanism via a carbenium ion, which usually takes place in protic solvents, and a carbene mechanism in aprotic solvents (Scheme 28). In both cases diazo compounds are intermediates, which can sometimes be isolated. ... 

The base catalyzed decomposition of arylsulfonylhydrazones of aldehydes and ketones to provide alkenes is called the Bamford-Stevens reaction. When an organolithium compound is used as the base, the reaction is termed the Shapiro reaction. The most synthetically useful protocol involves treatment of the substrate with at least two equivalents of an organolithium compound (usually MeLi or BuLi) in ether, hexane, or tetramethylenediamine. The in s/ft formed alkenyllithium is then protonated to give the alkene. The above procedure provides good yields of alkenes without side reactions and where there is a choice, the less highly substituted alkene is predominantly formed. Under these reaction conditions tosylhydrazones of a,(3-unsaturated ketones give rise to conjugated dienes. It is also possible to trap the alkenyllithium with electrophiles other than a proton. 

Other bases may be employed, e.g. lithium hydride, sodium hydride, sodium amide or sodium in ethylene glycol with sodium in ethylene glycol, the reaction is called the Bamford-Stevens reaction. Aldehyde tosylhydrazones (200) do not form dianions with organolithiums, but the reagent adds to the carbon-nitrogen double bond to give the dilithium derivative (201) which decomposes to the organolithium compound (202). 

Nortricyclanylidene (tricyclo[2.2.1.02,6]heptan-3-ylidene, 46) was originally generated via the Bamford-Stevens reaction of the corresponding 3-nortricyclanone p-tosylhydrazone sodium salt (49) (Scheme 9).126 The formation of quadricyclane (tetracyclo[2.2.1.02 6.03 5]heptane, 48) was anticipated, from an intramolecular... 

The Bamford-Stevens reaction of 2-vinylcyclobutanone tosylhydrazone sodium salt has been studied with respect to the potential carbene-carbene rearrangement expected to give ring expansion into a cyclohex-3-en-l-ylidene derivative compared to the 2-vinylcycloprop-ylidenecyclopent-3-en-l-ylidene rearrangement. ... 

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