Bamford-Steven reaction

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 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. 

Baeyer-Villager oxidation, 10, 151, 433 Bamford-Stevens reaction, 402 Barton reaction, 253 Beckmann rearrangement, 140 Benzilic acid rearrangement, 418, 435 3 -Benzoyloxy-7-methylenecholest-5-ene, 60 Benzylmagnesium chloride, 64 3-Benzyloxycholesta-3,5-diene, 342... 

From 5 the formation of alkene 2 is possible through loss of a proton. However, carbenium ions can easily undergo a Wagner-Meerwein rearrangement, and the corresponding rearrangement products may be thus obtained. In case of the Bamford-Stevens reaction under protic conditions, the yield of non-rearranged olefins may be low, which is why this reaction is applied only if other methods (e.g. dehydration of alcohols under acidic conditions) are not practicable. 

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>. 

Phosphoryl-substituted diazo compounds of general type 4 have recently been synthesized by amine diazotization, Bamford-Stevens reaction, and diazo group... 

The most frequent synthetic approaches, summarized in Scheme 4, are towards the primary photophores. The preparation of aryl azide derivatives follows the typical retro-synthetic pathway in the majority of the reported cases (Scheme 4 A), and, practically, diazotation is the most commonly used procedure [24 - 29]. In the case of diazirines only one major synthetic sequence is repeated ammonolysis of oximes followed by dehydrogenation (Scheme 4B) [30-32]. There are various ways of preparing diazo- or diazocarbonyl-compounds most frequently the Forster and Bamford-Stevens reactions (Scheme 4C) are employed [33-37]. 

The Bamford-Stevens reaction and the Shapiro reaction share a similar mechanistic pathway. The former uses a base such as Na, NaOMe, LiH, NaH, NaNHa, heat, etc., whereas the latter employs bases such as alkyllithiums and Grignard reagents. As a result, the Bamford-Stevens reaction furnishes more-substituted olefins as the thermodynamic products, while the Shapiro reaction generally affords less-substituted olefins as the kinetic products. 

Baeyer-Villiger reaction, 9, 3 43, 3 Bamford-Stevens reaction, 23, 3 Barbier Reaction, 58, 2 Bart reaction, 2, 10 Barton fragmentation reaction, 48, 2 Bechamp reaction, 2, 10 Beckmann rearrangement, 11, 1 35, 1 Benzils, reduction of, 4, 5 Benzoin condensation, 4, 5 Benzoquinones ... 

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]. 

The product hydrazide may be sulfonated and decomposed by heating with a base in ethylene glycol to yield benzaldehyde, CeHsCHO. Many aromatic aldehydes may be produced by similar routes. The hydrazone derivative of toluenesulfonic acid reacts with an aldehyde or a ketone in the presence of a base catalyst, such as sodium ethoxide, to yield the corresponding olefin (Bamford-Stevens reaction) ... 

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