Tosylhydrazones pyrolysis

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). 

The formation of the bridged product 191 was investigated using the cyclopentadiene system as a model. Thus, the salt of the tosylhydrazone 198 was prepared and thermolyzed in order to examine three possible variants of rearrangements (equation 62)75. Analysis of the reaction products 200-202 and their transformations [e.g. the pyrolysis of bicyclic triene 202 to cA-8,9-dihydroindene 203 (equation 63) rather than to product 200 or 201] allows one to conclude that the mechanism involves a transformation of carbene 188 into diradical 204 which can be the precursor of all the products observed (equation 64)75. An analogous conversion takes place via radical 205 in the case of carbene 199 (equation 65). 

The reactivity of cage-annulated carbene (53) was found to depend markedly on the method of its formation." Pyrolysis of the corresponding tosylhydrazone sodium salt gave products of intramolecular CH insertion or H-abstraction. Photolysis of a diazirine precursor gave only azine products by reaction of the carbene with the precursor or diazo compound. Treatment of the m-dibromoalkane with BuLi gave products due to intermolecular insertion of the carbene into CH bonds of the solvent. 

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... 

In a modified flash-vacuum-pyrolysis apparatus (Otto Fritz company, Hofheim, Germany) the Na salt of l-methylbicyclo[2.2.1]heptan-7-one tosylhydrazone (1 g, 3.2 mmol) was added in small portions over 1 h to silylated silica gel (2 - 3 g) in a preheated (250 "C) pyrolysis flask at 1 x 10 4-10 3 Torr. The volatile products (47-68%) were collected in a cooled [N2(1)J flask and were separated by preparative GC (Car-bowax + KOH on Chromosorb W, 4.5 m, 60 °C). 

In support of the above mechanism, spiro[cyclopropane-l,2 -(6 -methyienebicycIo[3.1.0]hexane)] (10) is indeed isolated from thermolysis of the sodium salt of 7-oxospiro[bicyclo[3.2.0]hept-3-ene-2,1 -cyclopropane] tosylhydrazone (9), presumably due to the fact that the corresponding homofulvene would be too strained to form.8 Additional support of the proposed mechanism is also provided by the pyrolysis of the sodium salt of [7,7-2H2]bicyclo[3.2.1]hept-2-en-6-one tosylhydrazone (11), which gives [7,7-2H2]-4-methylenebicyclo[3.1.0]hex-2-ene (12).8... 

S. Phenyldiazomethane (Vacuum pynolyzxa method). In a 200-mL, singlenecked, round-bottomed flask is placed 13.71 g (0.05 mol) of benzaldehyde tosylhydrazone. A 1.0 M solution (51 mL) of sodium methoxide in methanol (0.051 mol) (Note 2) is added via syringe and the mixture is swirled until dissolution is complete (Note 3). The methanol is then removed by rotary evaporator. The last traces of methanol are removed by evacuation of the flask at 0.1 mm for 2 hr. The solid tosylhydrazone salt is broken up with a spatula and the flask is fitted with a vacuum take-off adaptor and a 50-mL receiver flask. The system is evacuated at 0.1 nm and the receiver flask is cooled in a dry ice-acetone bath to about -50°C. The flask containing the salt is immersed in an oil bath and the temperature is raised to 90°C (use a safety shield). At this temperature, red phenyldiazomethane first begins to collect in the receiver flask. The temperature is raised to 220°C over a 1-hr period (Note 4). During this time red phenyldiazomethane collects in the receiver flask (Note 5). The pressure increases to 0.35 mm over the course of the pyrolysis. On completion of the pyrolysis the pressure drops to less than 0.1 mm. 

The present procedure uses sodium methoxide in methanol for generation of the tosylhydrazone salt. This procedure gives the highest reported yield and, unlike other procedures, also gives pure diazo compounds free from solvents. This vacuum pyrolysis method appears applicable to the formation of relatively volatile aryldiazomethanes from aromatic aldehydes. Table I gives yields of diazo compounds produced by this vacuum pyrolysis method. The yields have not been optimized. The relatively volatile diazo esters, ethyl a-... 

FORMATION OF DIAZO-COMPOUNDS BY VACUUM PYROLYSIS OF SODIUM SALTS OF TOSYLHYDRAZONES... 

The major limitation of the vacuum pyrolysis method appears to be thermal decomposition of less volatile diazo compounds during the pyrolysis. The vacuum pyrolysis method was unsuccessful for the preparation of 1-naphthyl diazomethane and 3,5-dichlorophenyldiazomethane. However, such diazo compounds could be prepared from the corresponding tosylhydrazone salts by pyrolysi s in ethylene glycol and extraction of the aryldiazomethane into... 

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. 

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... 

Pyrolysis of the sodium salt of the tosylhydrazone of 10-bicyclo[5.2.1 ]deca-none provides a remarkably easy synthesis of tricyclo [5.2.1.0 4>10] decane... 

Dehydroadamantanes are most readily obtained from either carbene insertion reactions or from 1,3-reductive eliminations. Pyrolysis of the dry sodium salt of the tosylhydrazone of adamantanone gives good yields of 2,4-dehydroada-mantane 133>. The unstable 1,3-dehydroadamantane is obtained from the treatment of 1,3-dibromoadamantane with sodium (Eq. (43)) 134>. 

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). 

The thermal isomerization of l-ethynyl-2-vinylcyclopropane 57 has been also reported. Thus, the dimer 59 was formed in the pyrolysis of the tosylhydrazone salt... 

Cycloheftatrienylidene 4). Unsubstituted 4 could be obtained by thermal or photochemical decomposition of tropone tosylhydrazone salt 19c) 35, 36), In the case of the dibenzo 19a) or tribenzo derivatives 19b), the diazocycloheptatrienes 20 a, b) could be isolated Then photolysis of 20 a, b gave 4 in these cases too. An interesting entry in the cyclohep-tatrienyhdene series consists of flash pyrolysis of phenyldiazomethane 21) followed by a rearrangement to 4 38). 

The pyrolysis and photolysis of this diazirine yield 1,1,2-trimethyl-cyclopropane, teri-butylethylene, and tetramethylethylene. The pyrolysis results are very similar to those obtained by the methanolysis of the analogous tosylhydrazone in an aprotic solvent, but differ appreciably from the photolytic data. These results are shown in Table V. Once again the results are consistent with the production of a hot carbene in the photochemical experiments. No details are at present available for the photolysis of this diazirine at low pressures, where, by analogy with other work, the isomerization of the trimethylcyclopropane would be expected to occur. 

The pyrolysis of tetramethylenediazirine in the gas phase is a first-order reaction yielding only cyclopentene and nitrogen. Similarly, the treatment of the tosylhydrazone of cyclopentanone with base under aprotic conditions yields cyclopentene as the only hydrocarbon product. Photolysis of this diazirine yields cyclopentene as the principal hydrocarbon product (99.2%), but very small quantities of bicyclo[2,1,0]-pentane (0.3%) and methylenecyclobutane (0.1%) are also formed. In addition, about 0.5% of another hydrocarbon was detected but not identified. Its early position of the chromatogram indicates that it may be a fragmentation product. 

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). 

Pyrolysis of tosylhydrazone salts and other deamination reactions of cyclobutane derivatives yield bicyclobutane (equation 30). ... 

Borden, W. T., Concannon, P. W., Phillips, D. I. Synthesis and pyrolysis of carbonate tosylhydrazone salts derived from vicinal glycols. Tetrahedron Lett. 1973, 3161-3164. 

Pyrolysis of lactone tosylhydrazone salts. Agosta et al.3 have developed a process that is formally a reversal of the Baeyer-Villiger oxidation, that is, a method for conversion of lactones into cyclic ketones. An example is the synthesis of the spiro[3.4]-octane-l-one (5). The starting material is the lactone (1) this is converted into the... 

The pyrolysis of tosylhydrazones 14 and 16 obtained from the corresponding ketones yields tricyclic products 15 and 17, respectively, via carbenic intermediates. Generation of the carbenes from 14 and 16 leads to preferential 1,3-migration of the trimethylsilyl group to the carbenic... 

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. 

Numerous unsuccessful attempts to synthesize cyclopropanethione have been reported. Thermal or photochemical generation of the C3H4S species from different sources always leads to allene episulfide. Some representative experiments include (a) in vacuo pyrolysis of the sodium salt of 2,2,4,4-tetramethylthietanone tosylhydrazone (4) into the stable tetramethylallene episulfide (S), (b) pyrolytic extrusion of nitrogen from perfluorinated thiadiazoline 6, (c) in vacuo pyrolysis of spiro compound 8 into methylenethiirane (3), (d) the flash vacuum pyrolysis-microwave spectroscopic approach applied to spiro compounds 9 and 10, (e) pyrolysis of anthracene adduct 11 and tosylhydrazide salt 12, (f) thermolytic nitrogen extrusion from pyrazoline-4-thione 13, thermolysis of tetramethylallene episulfide (5) or pyrazoline 13 in dig-lyme solution, and photolytic nitrogen extrusion from pyrazoline 13, ° (g) thionation of methylenecyclopropanone 15, and (h) reaction of donor-acceptor substituted allenes 18 with elemental sulfur. ... 

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