Tosylhydrazones reagents

P-Hydroxy tosylhydrazones, which are the products of a conventional aldol reaction between a dilithi-ated tosylhydrazone reagent and an aldehyde, can also be prepared by alternative routes. For example, Stork and Ponaras have described a procedure whereby an epoxy ketone is converted into an epoxy hydrazone. Subsequent addition of an alkyl- or aryl-magnesium bromide followed by hydrolysis yields either an a-alkyiated- or a-arylated-p-hydroxy ketone or an a,p-unsaturated ketone. Since the attack of the Grignard reagent on the epoxide occurs with inversion at the a-carbon, this reaction can be used to... 

The extent of olefin formation depends on the position of the functional group, " on the degree of a-substitution and on the concentration of the hydride (or deuteride). Usually olefin formation can be largely suppressed by increasing the concentration of lithium aluminum deuteride. With certain tosylhydrazones, however, such as the C-17 derivative (103), olefin (104) is a major product irrespective of the quantity of the reagent used. ... 

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 ... 

Of course, the key limitation of the ylide-mediated methods discussed so far is the use of stoichiometric amounts of the chiral reagent. Building on their success with catalytic asymmetric ylide-mediated epoxidation (see Section 1.2.1.2), Aggarwal and co-workers have reported an aza version that provides a highly efficient catalytic asymmetric synthesis of trans-aziridines from imines and diazo compounds or the corresponding tosylhydrazone salts (Scheme 1.43) [68-70]. 

This reagent was obtained either from Aldrich Chemical Company, Inc., or Lithium Corporation of America, Bessemer City, NC. A technical data sheet is available from the suppliers. Solutions of ca. 2 M were titrimetrically analyzed for active alkyllithium by the tosylhydrazone method. It is advisable to make certain that the organolithium reagent to be used was prepared in pentane solution. This evaluation can be easily accomplished by the gas chromatographic analysis of the organic layer obtained from the hydrolysis, under a nitrogen atmosphere, of the tert-butyllithium solution to be used. Isobutane and pentane should comprise essentially all of the... 

Regeneration of carbonyl compounds from certain derivatives. Ketones can be recovered in satisfactory yield from the phenylhydrazones, p-nitrophenyl-hydrazones, tosylhydrazoncs, oximes, and semicarhazones by reaction with 1 equivalent of (C6H,Se0)20. 2,4-Dinilrophenylhydrazones and N,N-dimethyl-hydrazones arc inert under even rather vigorous conditions. The reagent can also be used to regenerate aldehydes from oximes or tosylhydrazones. 

Reduction of tosyl- and trisylhydrazones.3 The reagent (1 equivalent) reduces tosylhydrazones of ketones to alkanes in yields of 60-85% (GLC). The reduction is Subject to sleric hindrance and so is not effective with the tosylhydrazone of camphor. Tosylhydrazones of aldehydes are reduced in moderate yield (about 50%). The reagent does not reduce tosylhydrazones of aromatic or a,/)-unsaturated aldehydes or ketones. 

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. 

The reduction of tosylhydrazones by complex metal hydrides has been used very effectively to prepare saturated steroid hydrocarbons in high yields.317 In certain cases this reduction (with lithium aluminum hydride) takes a different course, and olefins are formed.318 The effect is dependent on both the reagent concentration and the steric environment of the hydrazone.319 Dilute reagent and hindered hydrazone favor olefins borohydride gives the saturated hydrocarbon. The hydrogen picked up in olefin formation comes from solvent, and in full reduction one comes from hydride and the other from solvent. This was shown by deuteriation experiments with the hydrazone (150) 319... 

Hindered cuprates. A novel route to lithium dialkylcuprates containing a secondary or a tertiary alkyl group involves reaction of the tosylhydrazone of an aldehyde with a copper reagent, such as dilithium trimethylcuprate (6, 386 7, 115). An example is shown in equation (I) for preparation of a cuprate containing the t-butyl group.1... 

Alkene synthesis. A modified version of an earlier synthesis of alkenes from the tosylhydrazones of aldehydes and certain alkyllithium reagents (9, 472-473) employs the N-r-butyldimethylsilyl derivatives (1) of tosylhydrazones of a,f)-enals, which undergo only 1,2-addition of an alkyllithium at - 78°. The adducts (2) decom-... 

Catecholborane is a versatile reducing reagent, a mild and convenient alternative to the classical (Clemmensen, using acids and Wolff-Kishner, using bases) reduction procedure of tosylhydrazones. Regiospecific isomerization occurs during the reduction of a,(3-unsaturated carbonyl derivatives often leading to unique alkenes (Eqs. 134 and 135) 222-223> and allenes (Eq. 136) 224). 

Cleavage ofkeioximes. Ketoximes can be cleaved by aqueous bromine buffered with NaHCOs. Sodium hypobromite may be the actual reagent. The method can be used for cleavage of tosylhydrazones in this case yields are improved by added HMPT. ... 

Oxidation. Triphenylbismuth carbonate suspended in CH2CI2 is a heterogeneous oxidant for a variety of functional groups. Allylic alcohols are efficiently oxidized to the corresponding unsaturated aldehydes or ketones, even in the presence of a thiol, which is itself oxidized by this reagent to a disulfide, cis- and Irani-1,2-Glycols are cleaved to dialdehydes hydrazones are oxidized to diazocompounds oximes are cleaved to ketones and 1,2-dialkylhydrazines are oxidized to azo compounds. Phenylhydrazones, semicarbazones, tosylhydrazones, aromatic and aliphatic amines, enamines, and enol ethers are inert to 1. 

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