Rearrangement tosylhydrazones

The Bamford-Stevens decomposition of tosylhydrazones by base has been applied to steroids, although not extensively. It has been demonstrated that the reaction proceeds via a diazo compound which undergoes rapid decomposition. The course of this decomposition depends upon the conditions in proton-donating solvents the reaction has the characteristics of a process involving carbonium ions, and olefins are formed, often accompanied by Wagner-Meerwein-type rearrangement. In aprotic solvents the diazo compound appears to give carbene intermediates which form olefins and insertion products ... 

The reaction mechanism has been confirmed by trapping of intermediates 13, 14 and 15. Because of the fact that neither a carbene nor a carbenium ion species is involved, generally good yields of non-rearranged alkenes 2 are obtained. Together with the easy preparation and use of tosylhydrazones, this explains well the importance of the Shapiro reaction as a synthetic method. 

The aminoketone 1, required as starting material, can be obtained by a Neber rearrangement from a A -tosylhydrazone. Another route to a-aminoketones starts with the nitrosation of an a-methylene carbonyl compound—often in situ—to give the more stable tautomeric oxime 7, which is then reduced in a subsequent step to yield 1 ... 

Diazocycloheptatriene (1), generated from the sodium salt of tropone tosylhydrazone, reacts with electron-deficient acetylenes to give H- 1,2-benzodiazepines 4 in moderate yield. It is suggested that the primary adducts 2 rearrange via the intermediates 3 to the products 4.114... 

In the case of sodium 2-(diarylmethylene)cyclopentanone tosylhydrazones 3, however, thermolysis gives the 3//-1,2-benzodiazepines 6 in good yield selected examples are shown. It is suggested that steric constraints in the diazo compounds 4 favor the [1,7] ring closure. The reaction proceeds by way of the intermediates 5, which rearrange to the products by a [1,5] shift of hydrogen.115... 

The most common rearrangement reaction of alkyl carbenes is the shift of hydrogen, generating an alkene. This mode of stabilization predominates to the exclusion of most intermolecular reactions of aliphatic carbenes and often competes with intramolecular insertion reactions. For example, the carbene generated by decomposition of the tosylhydrazone of 2-methylcyclohexanone gives mainly 1- and 3-methylcyclohexene rather than the intramolecular insertion product. 

Scheme 6.114, a carbene-carbene rearrangement transforms diphenylcarbene to o-phenylphenylcarbene, which is the progenitor of 565. Two phenylbicydo[4.1.0]-hepta-2,4,6-trienes and l-phenyl-l,2,4,6-cycloheptatetraene (562) have to be assumed as further intermediates. The participation of 562 is supported by the structure of the products 563 and 564, which should result from the addition of 562 to diphenylcarbene and the dimerization of 562, respectively. By thermolysis of the sodium salt of 2-phenyltropone tosylhydrazone, 562 was generated directly. At 100 °C in diglyme as solvent, 564 was identified as the only product and at 340°C/4Torr in the gas... 

A little-explored route to allenylsilanes utilizes tosylhydrazone derivatives of tri-methylsilyl alkynyl ketones [52]. Treatment with NaBH3CN in acidic medium leads to transient propargylic diazines, which rearrange with loss of nitrogen (Eq. 9.44). 

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). 

An interesting degenerate rearrangement was observed when in attempts to prepare the 5-diazomethyl-4-alkoxycarbonyl-l,2,3-thiadiazole (167) from its precursor, the tosylhydrazone 165 or the oxime 166, not 167 but the rearranged 5-(o -alkoxycarbonyldiazomethyl)-l,2,3-thiadiazole (168) was obtained (Scheme IV.65) [82TL1103 83JCS(CC)588]. 

This procedure appears to be general for the preparation, without rearrangement, of lesser substituted olefins. 2-Methyl-cyclohexanone tosylhydrazone gives 3-methylcyclohexene (98% yield by gas chromatography analysis).8 Cholestan-6-one tosylhydrazone gives A6-cholestene (95% isolated yield), androstan-... 

Donor-substituted 1-aminomethylcyclopropanes 108 110 and tosylhydrazones of 1-donor-substituted cyclopropyl ketones 111 can undergo ring enlargement to cyclobutanones through deamination. To this purpose, aminomethylcyclopropanes were diazotized with sodium nitrite 108-110 or isopentyl nitrite 109 in acidic medium and tosylhydrazones were decomposed in basic medium.111 The rearrangements proceed via diazonium ions and are especially useful for the construction of bicyclic systems. For examples of these rearrangements see 1,108 2,109 3,109 4,110 5,111 6 and 7.1 1... 

Thermal decomposition of y-lactone tosylhydrazone sodium salts are reported to yield cyclobu-tanones, which can be accounted for by rearrangement of an intermediate oxycarbene. In this manner, the sodium salts of dihydrofuran-2(37/)-one tosylhydrazones 1 were decomposed as a loose powder, at 310 C in a bulb-to-bulb distillation apparatus at an initial pressure of 0.1 Torr, to give the corresponding cyclobutanones 2 in addition to enol ethers, cyclopropanes and open-chain alkenes. Condensable products (74-76%) were collected at — 78 °C, weighed and the ratio of components was determined from their relative GC peak areas.63... 

Bicyclo[2.2.1]hept-7-yl cations, formed via the corresponding diazonium ions by diazotization of bicyclo[2.2.1]heptan-7-amine derivatives, rearrange partially to give bicyclo[3.2.0]heptanes (Houben-Weyl, Vol. 4/4, pp 106-107). Related diazonium ions can also be formed by irradiation of bicyclo[2.2.1]heptan-7-one tosylhydrazones in diluted sodium hydroxide and rearrange to form predominantly bicyclo[3.2.0]heptan-e. o-2-ols. On photolysis, the hydrazone 17 in 0.2 M sodium hydroxide gave t> <7o-2-methylbicyclo[3.2.0]heptan-exo-2-ol (18) with 77% selectivity and in 72-78% overall yield (GC).68... 

Intermediate diazonium ions as precursors of carbocations which can rearrange in the manner discussed are also formed in the photolyses of arylsulfonylhydrazones in basic medium. The photolysis of the optically active bicyclo[2.2.1]hept-5-en-2-one tosylhydrazone in 0.5 M sodium hydroxide gave bicyclo[3.1.1]hept-3-en-2-ol (25) in 6% yield with only 5% of retention of the optical activity, which indicates an achiral ally cation as the product-determining intermediate.84... 

As discussed, electron-donating groups at Cl in bicyclo[2.2.1]heptane systems promote the rearrangement to bicyclo[3.1.1]heptane derivatives. Photolysis of 1-methyl bicyclo[2.2.1]heptan-2-one tosylhydrazone in 1,2-dimethoxyethane in the presence of sodium hydroxide gave 2-methyl-bicyclo[3.1. l]heptan-2-ol (26a) in 7.5% yield in addition to bicyclo[2.2.1]heptane derivatives, while the 1-phenyl derivative gave the ring-contracted product 26b in only 2% yield.91... 

Since the first report in 1960 of the observation that sodium methoxide induced carbenoid decomposition of cyclobutanone tosylhydrazone (1) at 180 °C in either bis(2-ethoxyethyl) ether or /V-methylpyrrolidone results in an intriguing ring contraction to produce methylenecyclopropane (3),1 many experimental results have been presented invoking cyclobutylidene (2) as a key intermediate in this rearrangement. 

Recently, an experimental reappraisal of this rearrangement was reported, in which cubyl phenyl ketone tosylhydrazone (1) was thermolyzed in an ethanolic sodium ethoxide solution to give a good yield of a 1.5 1 mixture of 9-ethoxy-9-phenylhomocubane (3) and 9-ethoxy-l-phenylhomocubane (4).3 In addition, photolysis (mercury arc, Pyrex filter) of cubylphenyldi-azomethane (2) in ethanol also produced a similar result.3... 

Tosylhydrazones of a,/ -unsaturated ketones can give dienes on treatment with lithium aluminum hydride, but normally rearranged mono-olefins are formed.318 Again, a vinyl carbanion intermediate is suggested by deuterium incorporation studies.290 Reaction with alkyl lithium gives high yields of dienes 325 tosylhydrazones of A4-3-ketones give A2,4-dienes ... 

VII. 14(13 -> 12aH)y46eosteroids (C-Nor-D-Homo Steroids) / 400 By solvolysis of 12/ -methylsulfonyloxy steroids / 400 By fragmentation-rearrangement of 12-tosylhydrazones / 402... 

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