N-Tosylhydrazones

All three compounds (WF6 and MoF6 are best) will bring about a reaction (not a fluorination) that may have synthetic utility at 0CC in l,l,2-trichloro-l,2,2-trifluoroethane (Freon 113) or chloroform they will cleave N,TV-dimethyl- and N-tosylhydrazones and oximes back to the parent carbonyl compounds12,14 (UF6 converts any first-formed aldehydes into acid fluorides1213). All three hexafluorides will convert1215 tertiary amines into carbonyl compounds and carboxylic acids into acid fluorides.16 They also dope polyacetylene to the metallic regime.17... 

Indazoles were prepared by many different methods. Indazoles 41 were synthesized from nitroaromatics 39 and N-tosylhydrazones 40 with bases (14CC5061). A rhodium(III)-catalyzed oxidative olefination of 1,2-di-substi-tuted arylhydrazines with alkenes via sp C-H bond aaivation followed by an intramolecular aza-Michael reaction yielded indazoles (140L2494). Copper-catalyzed C-H amidation with aromatic imines 42 with tosyl azide provided a route to 3-substituted indazoles 43 (14OL4702). 4,5,6,7-Tetrahydro-lH-inda-zol-3-(2fJ)-one derivatives were prepared in two-step one-pot process (14SC1076). A regioselective synthesis of 2H-indazoles 45 was achieved using... 

Xja Y, Liu Z, Xiao Q et al (2012) Rhodium(II)-catalyzed cyclization of bis(N-tosylhydrazone) s an efficient approach towards polycyclic aromatic compounds. Angew Chem Int Edit 51 5714-5717. doi 10.1002/anie.201201374... 

For the stereoselective synthesis of aminoethers, the N-tosylhydrazones proved to be a good choice [104] and when this process was transferred to the homochiral imine 318, the trons-aminoether 319 was obtained in high yield and respectable enantioselectivity [105]. 

Benzeneseleninic anhydride oxidizes hydrazines to azo-compounds and hydrazones to acylazo-compounds. Azo-compounds have also been synthesized by photolysis of iminophosphoranes, reaction of hydrazones with allyl acetate under nickel catalysis/ reaction of A/-methyl-N-tosylhydrazones with amines/ and deoxygenation of azoxy-compounds/ ... 

A liimtation of the current protocol is the use of diazo compounds, which are potentially explosive and not readily available. The inherent hazards in handling these diazo compounds severely limit the practical apphcation of this methodology. In 2001, Aggarwal and coworkers disclosed a modified Bamford-Stevens reaction [29] for the in situ generation of diazo compound from N-tosylhydrazone salts. The addition of BnEtsN CT as a phase-transfer catalyst can enable the diazo compound to be produced at 30-40°C (Scheme 20.12) [30]. 

The method of in situ generation of diazo compounds from N-tosylhydrazone salts proved to be quite efficient for aziridination. When sulfide 19 was employed as a catalyst, moderate to good yields and excellent enantioselectivities were obtained with a range of aromatic imines. The trans cis ratios of the products varied in the range of 2-8 1, dependent on the N-protecting group of imines. Notably, the aziridinations of aliphatic imines (cyclohexyl imine, tert-butyl imine) and benzophenone-imine also proceeded well, giving the aziridine products in 50-53% yields and 73-98% ee [39]. 

Abstract In this chapter, alkene synthesis based on the reactiOTi of //-tosylhydrazones is described. The reactivity of tosylhydrazones is determined by either the acidity of a-proton and hydrazcMie proton or the electropositivity of the carbon of C=N bond. This leads to diverse reactivities and a series of N-tosylhydrazone-based olefination methodologies. Both non-catalytic and transition metal-catalyzed olefinations from Al-tosylhydrazones are introduced in this chapter. Most of the transition metal-catalyzed reactions proceed via metal carbene transformations. The synthesis of alkenes through Pd-catalyzed cross-coupling reactions of Af-tosylhydrazones is particularly attractive and will be discussed in detail. 

For the reaction of N-tosylhydrazones derived from chiral cyclic ketones, the regioselectivity is also well controlled by the substrate structrrres. Barluenga and coworkers reported the synthesis of several enantiomericaUy enriched aUyUc ethers without chirality erosion through the coupling of aryl halides with a-chiral cyclic N-tosylhydrazones under the similar reaction conditions (Fig. 20) [99]. 

The scope of transition metal-catalysed cross-coupling reactions involving N-tosylhydrazones has been broadened. While IV-tosylhydrazones cross-couple with trialkylsilylethynes to form C -C s bonds under Cu(I) catalysis,i° Pd(0) catalysis has been used to induce (i) their oxidative cross-coupling reactions with allylic alcoholsi and (ii) their cross-coupling with cyclopropyl halides, giving rise to... 

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