Tosylhydrazone lithium salt

The thermochemistry of 4,4-diphenylcyclohexa-2,5-dienylidene (lu) in solution was investigated by Freeman and Pugh (Scheme 19).106 The thermal decomposition of the diazo compound 2u (produced in situ from the corresponding tosylhydrazone lithium salt) produces a complex product mixture with the azine as the major product (51%). Volatile monomeric products biphenyl and several terphenyls were also formed in low yields. 

Phenyl(trimethylsilyl)carbene (21) has been generated from phenyl(trimethylsilyl)diazo-methane (20) by gas-phase pyrolysis39,40 as well as by thermolysis97 or photolysis33,40,98,99 in solution, by flash thermolysis of the tosylhydrazone lithium salt 18040, and by pyrolysis... 

Tetramethyl-3-oxetanylidene (365) and thietanylidene (366) have been generated by thermolysis of tosylhydrazone lithium salts 422 The former ring opens, but the latter isomerizes to a methylenethiirane, thereby paralleling the behavior of cyclobutylidene423 (Eqs. 114-115). ... 

The same type of reaction occurs in the work of Hauptman (76T1293), who, studying the chemistry of diethynylcarbenes, found that the pyrolysis of the lithium salts of diethynylketone tosylhydrazones 5 (140-150°C) in the presence of olefins leads to cyclopropanes. This process results in the formation of the corresponding 3-ethynylpyrazoles. The formation of l-p-tolylsulfonyl-3-alkynylpyrazoles from hydrazone runs in milder conditions (50°C, 14 h) (Scheme 24). 

Carbenes are known intermediates in the thermolytic or photolytic decomposition of the lithium or sodium salts of tosylhydrazones, which, for endocyclic carbenes, results in ring contraction when the elimination of / - or y-hydrogens is impeded. Simple cyclobutanes generally cannot be prepared by this route from monocyclic cyclopentanone tosylhydrazones. However, the lithium salt of bicyclo[2.2.1]heptan-7-one tosylhydrazone gave bicyclo[3.2.0]hept-l-ene (4) as the major product (74%) by vacuum pyrolysis at 185 JC/20 Torr, together with bicyclo[2.2.1]heptane (14%) and tricyclo[2.2.1.02,7]heptane (12%) in 80% overall yield.67... 

The lithium salt of an active hydrogen compound adds to the lithium salt of the tosylhydrazone of an aldehyde to give product 49, If X = CN, SPh, or S02R, 49 spontaneously loses N2 and LiX to give the alkene 50. The entire process is done in one reaction... 

The pyrolysis at 140-150 °C of the lithium salts of diethynyl ketone tosylhydrazones 33 led to the formation of the triplet diethynylcarbenes 34 which were trapped by olefins to give, in a nonstereospecific reaction, the 1,1-dialkynylcyclopropane derivatives 35 a, b, Eq. (11)24). 

Thermolysis of the lithium salt of the tosylhydrazone of 2-isopropylidene-4,4-dimethyl-3-thietanone gives 2,3-bis(isopropylidene)thiirane. Treatment of 2-methylene-3-thietanones with thionyl chloride effects addition of chlorine across the carbon-carbon double bond. Radical ions of 4-methylene-2-thietanethiones have been obtained by electrolysis and examined by electron-spin resonance ... 

Thus, addition of dichloroketene to cyclohexene gave 8,8-dichlorobicyclo[4.2.0]octan-7-one in 39% yield which underwent dehalogenation upon treatment with zinc in acetic acid at room temperature for 24 hours to give the corresponding cyclobutanone. Pyrolysis of the dry lithium salt of its tosylhydrazone at 120-180°Cat0.1 Torr produced a 2 1 mixture of isomeric methylenecyclopropanes 42 and 43 in 50% yield. 

The olefinic aldehyde 6a (58 mg, 0.26 mmol) and 4-toluenesulfonohydrazide in dry benzene (25 mL) was placed in a 5-mL flask equipped with a Dean-Stark water separator. The mixture was refluxed under dry Nj for 5 min. The solvent was removed and replaced by dry THF (2.5 mL) and 2 M BuLi in hexane (0.13 mL, 0.26 mmol) was added to the stirred solution. After 30 min the solvent was removed and the residual lithium salt of the tosylhydrazone 6b was heated slowly under reduced pressure (0.25 Torr). Between 120°C and 140°C the 4,5-dihydro-3/f-pyrazole 7 was collected as a colorless oil yield 50 mg (81% based on the aldehyde) nl 1.5042 [a] -I-95 (c = 1.0, CHCI3). A solution of the 4,5-dihydro-3i/-pyrazole 7 in Et20 (35 mL) was irradiated in a Rayonet reactor using 3500 A lamps and a Pyrex filter for 1 h. Removal of the solvent followed by distillation (airbath temperature, 80 °C) of the residual oil under reduced pressure (0.3 Torr) afforded pure (— )-cyclocopacamphene (8) yield 30 mg (93%) [a]o — 42 (c = 1.1, CHCI3). 

New examples of the photodecomposition of sodium and lithium salts of p-toluenesulphonylhydrazones to give carbenes, by way of unstable diazo intermediates, have again been reported. Benzocyclobuten-1-ylcarbene, 2-methyl-benzocyclobutenylidene, and o-styrylcarbene have been prepared in this way from the sodium salts of the tosylhydrazones of benzocyclobutene-l-carboxaldehyde, 2-methylbenzocyclobutenone, and o-formylstyrene, respectively. Similarly, 5-norbornen-2-one tosylhydrazone (154) is converted on irradiation in aqueous sodium hydroxide solution into 5-norbornen-2-ol (155) and nortricyclanol... 

The tosylhydrazone (88 X = O) decomposes in the gas phase to the carbene (89), which cyclizes to a mixture that contains mainly the dihydrobenzofuran (90) and dihydrobenzopyran (91) and in which the former predominates in the case of the sulphur analogue (88 X = S) the ratio of the two types of product is reversed. The lithium salt (92) of the 2-methyleneaIlyl dianion reacts with o-phthalaldehyde to yield the dihydroisobenzofuran (93), together with the methylenebenzocycloheptanediol (94). A mixture of the positional isomers (96 ... 

Jones developed a new fascinating method for [n]paracyclophane synthesis based on spiro carbene rearrangement. The first synthesis of la was achieved two decades ago by this method through rearrangement of the carbene species generated by thermolysis of the lithium salt of the spiro dienone tosylhydrazone 6 (Scheme 1) [1]. Although this work was epoch-making as the first synthesis of la, the formation of by-products hampered further study of la. 

Only one of the methods used for the synthesis of [6]paracyclophanes was also successful in generation of the lower homologue, [5]paracyclophane (2a) (Structures 1), indicating clearly the limitation of these methods thus FVP of lithium salt of tosylhydrazone 20 [3f], thermolysis of [5.2.2]propelladiene (21a)... 

A synthesis of [6]paracyclophane has been reported which involves flash pyrolysis of the lithium salt of tosylhydrazone (119). Authentic samples of diketones (120) have been prepared by lead tetra-acetate oxidation of the corresponding tricyclic diols. ... 

Pyrolysis of the dry lithium salt of the tosylhydrazone of 2-methylnorbornen-7-one affords, by way of 2-methyl-7-norbomenylidene, the following products of fragmentation and rearrangement (relative proportions) 2-methylcyclohexa-l,3-diene (1.4), 2-methylnorborn-2-ene (1.0), (427) (8.9), (428) (4.8X and (429) (2.8) as well as three unidentified compounds. The first, second, and fifth (429) named products are analogous to those formed from 7-norbomenylidene. The dominance of (427)... 

Nickon investigated the 1,2-hydrogen shifts in thermal and photic Bamford-Stevens reactions of cyclohexanones. Under eonditions known to favor the Shapiro reaction, tosylhydrazone 18a afforded the two expected alkenes 19 and 20 as well as an unexpected product (identified as 21) in a ratio of 15 60 25. Under conditions known to favor the Bamford-Stevens reaction, lithium salt 18b was subjected to thermolysis (neat, 170 °C) and also to photolysis (pentane suspension, -70 °C). Under both sets of conditions the three products 19, 20 and 21 were formed in approximately the same ratio (84 4 12 and 83 6 11), thus demonstrating the switching of major alkene product from 19 to 20 on moving from the Shapiro reaction to the Bamford-Stevens reaction. 

Deprotonation of TosyIhyd razones. The deprotonation of to-sylhydrazones with LHMDS provides the corresponding lithium salts, which can be further decomposed into the diazo intermediates. The addition of late transition metal complexes leads to the formation of metal carbenoid species which undergo various reactions, such as cyclopropanation, aziridination, epoxidation, and C-H insertion. For instance, the lithium salt of tosylhydrazone 2, prepared from LHMDS, is reacted with an imine or an alkene in the presence of rhodium(II) acetate and a chiral sulfide to give respectively, the corresponding aziridine or cyclopropane derivatives (eqs 36 and 37). Under similar reaction conditions, the sodium salt prepared from NHMDS works equally well. 

Hindered cuprates, conjectured to be of the type (4), which cannot be formed by normal methods, can be prepared from the bromomagnesium or lithium salts of tosylhydrazones of secondary or tertiary aldehydes by reaction with suitable mixtures of alkyl-lithiums and cuprous iodide. Alkylation of the cuprates furnishes high yields of branched alkanes (e.g. Scheme 9). Tosylhydrazones of primary or aromatic aldehydes give very low yields of hydrocarbons, or none at all. 

The sodium salt of cyclopropanecarboxaldehyde tosylhydrazone (157) behaves similarly on heating to 125 135°C. Labelling experiments using the lithium cyclopropanecarboxaldehyde-p-tosylhydrazone salt has proved the occurrence of a cyclopropylcarbene-cyclobutene C3 - C4 ring expansion instead of a simple intramolecular carbene insertion in one of the four C-H bonds and bicyclobutane ring-opening . For other examples and discussion of such a rearrangement see Ref. 189. In an apparently related reaction, when cyclopropylmethyl tosylate (158) is treated with potassium t-butoxide in dimethyl sulphoxide at room temperature for 1 h, a quantitative mixture of cyclobutene and methylenecyclopropane is produced in equal amounts (equation 110) °. 

Ring contraction of cyclobutylidenes is known, but not so widely explored. Thus, pyrolysis (200°C) or irradiation of the lithium or sodium salt of cyclobutanone tosylhydrazone (262) gave the 2-vinylcyclobutylidene (263) which then rearranged mainly to ring contraction products (equation 181). 

As expected, the presence of Cu promotes addition to the lithium and magnesium salts of secondary and tertiary aldehyde tosylhydrazones. Diliihiotrialkylcuprates react with tosylhydrazones (130) to generate in high yield hin r cuprates (131), which imdergo typical cuprate reactions (Scheme 25). 

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-... 

Such a cation effect has not been observed for the ruthenium-porphyrin-catalyzed intramolecular carbenoid C-H insertion of tosylhydrazones. The lithium and the sodium salts provided equally good results, although the use of LHMDS has been preferred by the researchers (eq 39). ... 

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