Tosyl hydrazone salt

Carbenes of type (113), generated by thermal decomposition of the appropriate tosyl-hydrazone salts, undergo ring opening more readily when the ring heteroatom is oxygen rather than when it is sulfur (78JA7927). 

In 2001, a modified procedure for sulfur ylide-catalyzed epoxidation, aziridination and cyclopropanation was introduced by Aggarwal and co-workers that utilized the generation of the diazo compounds in situ from tosyl hydrazone salts at 40 °C in the presence of a phase-transfer catalyst [46, 79]. (For experimental details see Chapter 14.12.1). Using this modified protocol, sulfide 4 was shown to be effective for epoxidation and aziridination (see Sections 10.2.1.4 and 10.3), but was not an effective cyclopropanation catalyst (see Table 10.3). Sulfide 28 was tried instead as it had been shown in achiral studies [96] that six-membered sulfides were more effective than five-membered analogues. This change gave rise to... 

The preparation of other Step 1 oxirane tosyl hydrazone salts is provided (1). 

Epoxidations were also performed using lithium or ammonium benzaldehyde tosyl hydrazone salts as described by the author. 

The protic reaction on occasion is a useful method of alkene formation, but is far from general because the cation intermediate tends to undergo rearrangements.Further, even for cases in which elimination to an alkene is the predominant pathway, the regioselectivity of the process is often mediocre. A key step in the synthesis of (+)-a-eudesmol and (-)-a-selinene exemplifies this point (Scheme 60). There are, however, isolated examples of excellent selectivity, such as the reaction of a 3-ketotetrahydrofuran tosyl-hydrazone salt to give the corresponding cyclic enol ether as the major product (Scheme 61), the intro-... 

Acrylcarbenes can be generated in the gas-phase by p Trolysis of aldehyde tosyl-hydrazone salts, aryldiazomethanes 52-54) or 5-aryltetrazoles 55-57), Xhe immediate carbene precursor is in each case... 

The ylide, of general structure (4.132), is formed by reaction of the corresponding sulphide (4.133) with a metallocarbenoid resulting from transition metal salt-mediated decomposition of a diazo compound (4.134) or N-tosyl hydrazone salt (4.135). Reaction of the sulfonium ylide (4.132) with aldehyde (4.136) yields the trans-epoxide (4.137) as the major product and sulfide (4.133) which is then returned to the catalytic cycle (Figure 4.10). 

This reaction proceeds with high ee using aromatic aldehydes such as benzalde-hyde (4.138) and derivatives using tosyl hydrazone salt (4.139) and thus has utility in the synthesis of enantiopure stilbene oxide derivatives. High ees are also obtained with some heteroaromatic aldehydes such as 2-furaldehyde (4.140). Basic heteroaromatic aldehydes are poor substrates and the reaction proceeds with low yield and/or diastereoselectivity using aliphatic aldehydes and most a,(3-enones as substrates. These limitations have been overcome using a stoichiometric variant of this process. 

Thus increased yields, diastereo- and enantioselectivities are observed with the thianes. The ylides can be formed from halides, diazo compounds, or from tosyl-hydrazone salts via diazo compounds as shown above [168-170],... 

With Ai-tosyl-hydrazone salts as diazo precursors the best results were achieved using sulfide 302 as catalyst, with loadings of 5 mol%. The formation of trans-aziridines is favoured, and the diastereoselectivity is moderate to good, the enanti-oselectivity excellent. The process can be applied to a broad range of electrophiles and diazoprecursors, examples are given in the Table 7.24 [170, 171]. 

On photolysis or thermolysis of the peri-methylmercapto-substituted sodium salt of a-naphthaldehyde tosyl hydrazone 77 or diazomethyl-naphthalene 78, 2//-2-methylnaphtho[frc]thiophene 80 (83JA6096) is formed in 20% yield. Ylid 79 may be a predecessor of thiophene 80. In... 

Tosyl hydrazone lithium salt was prepared as the product of Step 1. 

A solution of copper(II)acetylacetonate (5 mg), 4-chloro-benxaldehyde and tosyl hydrazone lithium salt (2.5 eq) were mixed and heated to 45 °C 3 hours, cooled, and 1ml EtOAc/water, 1 1, added. The epoxide was isolated as a white solid in 54% yield with a trans/cis ratio of 2.8 1, respectively. 

The Neber rearrangement involves the base-catalyzed conversion of oxime tosylates, quaternary salts of hydrazones or /V-chloroimines to a-amino ketones via isolable azirine intermediates (equation... 

As masked diazo compounds the salts of tosyl hydrazones can react thermally and photochemically ( Bamford-Stevens-reaction ) to give alkenes (Scheme 3, variable... 

The fragmentation of 2-heterosubstituted 4,7-dihydro-1,3-dithiepins (232)-(234) viacarbene (235) gave 1,3-butadiene and carbon disulfide. The tosylhydrazone (232) was synthesized by cyclization of l,4-dichlorobut-2-ene with the 5,5 -sodium-potassium salt of dithiocarbonic acid-tosyl-hydrazone, the diazo compound (233) was synthesized by careful pyrolyzation of the dry Na salt of (232), and the trithiocarbonate (234) was synthesized from l,4-dichlorobut-2-ene and potassium trithiocarbonate in DMSO. Similarly, pyrolysis of the sodium salt of benzoannelated dithiepin (236), obtained in a one-pot synthesis from a,a -dichloro-o-xylene, carbon disulfide, potassium hydroxide, and tosylhydrazide gave o-quinodimethane, which could be trapped by dienophiles, such as acrylonitrile, to give Diels-Alder product (238) (Scheme 40) <92SCi7ii>. 

The generation of carbenes by the thermolysis of lithium or sodium salts of tosyl-hydrazones continues to provide interesting chemistry. The selectivity exhibited by 7-bicyclo[2,2,l]hept-2-enylidene (generated from the corresponding tosylhydrazone) is quite the opposite to that expected from theoretical predictions and earlier studies. Addition to 3,3-dimethylbut-l-ene affords the syn-isomer (118) as the major adduct and consequently any carbene-7i interaction resulting in bridge bending cannot of itself dominate the stereoselectivity of addition. Furthermore, the intramolecular insertion products of 2-methylbicyclo[2,2,l]hept-2-en-7-ylidene have been characterized and, from the product ratios, the species behaves as a true carbene. A 3-furyl-... 

Reaction of 2,6-dimethyl-l,4-benzoquinone with the quinomethyl carbanion derived from 2,3-dimethyl-1,4-naphthoquinone is reported to give the tricyclo-[6,3,l,0 ]dodecane derivative (749). Pyrolysis of the sodium salt of the tosyl-hydrazone of 7-cycloheptatrienylmethyl methyl ketone in diglyme at 150 C afforded (750 7%) similar pyrolysis of the tosylhydrazone salt from l-(7-cycloheptatrienyl)-ethyl methyl ketone gave (751 9 %). Both compounds are examples of the previously... 

Precursors for this task were obtained by addition of /-butylmagnesium bromide to the central bond of [1.1.1 ]propellane 40a followed by conversion of the 3-f-butylbicyclo[ 1.1.1 Jpentyl-1 -y 1-magnesium bromide (88) into the ketones 89 by standard methods.27 Reaction of ketones 89 with tosyl hydrazide afforded the hydrazones 90, which gave the corresponding lithium salts 91 by reaction with MeLi in ether. These salts were dried under high vacuum and then pyrolized at 4 x 10 5 torr in the temperature range of 100-130°C and the volatile products condensed in a liquid nitrogen-cooled trap. 

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