Tosylhydrazones also

The generation of phenylcarbene (512) and p-tolylcarbene at 250 °C/40Torr in the gas phase brought about only the ring expansion to give 5 and 10, respectively and their dimerization yielding 522 and 557 (Scheme 6.113). The co-thermolysis of the sodium salts of benzaldehyde and p-methylbenzaldehyde tosylhydrazone also gave rise to the mixed heptafulvalene 556. With a ratio of 1 2 1, the amounts of 522, 556 and 557 verified the expectation based on statistics [212]. 

Annulation Reactions. Larock et al. have described the synthesis of different heterocyclic systems using a [3+2] annulation approach. For instance, pharmaceutically important pyrido[l,2-fl]indole derivatives such as 93 are easily accessible from 2-substituted pyridines and aryne precursors (Scheme 12.48) [83]. More recently, the 1/f-indazole skeleton has been accessed through a [3+2] annulation from arynes and hydrazones. The reaction with Al-arylhy-drazones leads to 1,3-disubstituted indazoles 94 through an annulation-oxidation process (Scheme 12.48). The use of iV-tosylhydrazones also affords 3-substituted-Ai(H)-indazoles, although probably via a [3+2] cycloaddition (see Scheme 12.18) with in situ generated diazo compounds [84]. 

The reduction of a,jS-unsaturated ketones to olefins may also be effected via the tosylhydrazones (see section XI-A). 

Cu(N03)2, Bentonite, hexane, acetone, 60-97% yield." When silica gel is used as the support, tosylhydrazones and thioketals are also cleaved in excellent yield."... 

Zr(03PCH3), 2(03PC6H4S03H)o8, acetone, water, reflux 30 min-24 h, 70-95% yield. Semicarbazones, tosylhydrazones, and hydrazones are also cleaved."... 

Benzaldehyde was also treated with a range of tosylhydrazone salts (Table 1.5). Good selectivities were generally observed with electron-rich aromatic salts (Entries 1-3), except in the furyl case (Entry 7). Low yields of epoxide occurred when a hindered substrate such as the mesityl tosylhydrazone salt was used. 

The N-aminoaziridine version7 of the a,/3-epoxyketone->alkynone fragmentation is a possible alternative in situations where the simple tosylhydrazone version6-9 fails. The tosylhydrazone method often gives good yields at low reaction temperatures, but it tends to be unsuccessful with the epoxides of enones that are not cyclic or are not fully substituted at the /5-carbon atom. For example, it has been reported9 that 2,3-epoxycyclohexanone docs not produce 5-hexynal by the tosylhydrazone route. The A-aminoaziridine method can also be recommended for the preparation of acetylenic aldehydes as well as ketones. 

The l,3-dithian-2-ylidene substituted carbene (54), accessible from the tosylhydrazone (53) by a Bamford - Stevens reaction, not only participates in cycloaddition reactions but is also a source of 4,8-dithiaspiro[2.5]oct-l-ene 6JCS(P1)2773>. 

The reduction of tosylhydrazones by LiAlH4 or NaBH4 also converts carbonyl groups to methylene.277 It is believed that a diimide is involved, as in the Wolff-Kishner reaction. 

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. 

For the performance of intermolecular reactions of 5, its generation from the sodium salt of tropone tosylhydrazone (517) and from halo-1,3,5-cydoheptatrienes (518) are most suitable, but other precursors can also be employed, as illustrated in Scheme 6.105. In view of the product structures, some reactions of 5 give results that deviate from those of typical allene processes, and this is even valid for the dimerization (Scheme 6.105). 

In keto steroids the reductions were also achieved by electrolysis in 10% sulfuric acid and dioxane using a divided cell with lead electrodes (yields 85-97%) [862], hy specially activated zinc dust in anhydrous solvent (ether or acetic anhydride saturated with hydrogen chloride) (yields 50-87%) [155, 86J], and by the above mentioned reduction of tosylhydrazones with sodium borohydride (yields 60-75%) [811]. 

An exceptionally interesting example of an intramolecular [3 + 2] cycloaddition, in which the diazo dipole and the olefinic C=C bond are separated by only one carbon atom, is outlined in Scheme 8.65. The thermal decomposition of the allenic tosylhydrazone sodium salt 267 produced 1,4-dihydropyridazine 269 (57). It is assumed that diazabicyclohexene 268 is a short lived reaction intermediate. This suggestion is supported by the observation that the generation of the diazocumulene l-diazo-2-methyl-l-propene in the presence of 3,3-dimethylcyclopropene also leads to 269. 

Compound 2 is also formed by photolysis of the tosylhydrazone sodium salt of bicyclo[2.2.1]hept-2-ene-7-one. In methanol with sodium methoxide, the initially formed norbornenylidene accepts a proton to give the norbornenyl cation and subsequently gives 2 and 3 in a 16 84 ratio.9... 

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... 

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... 

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... 

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-... 

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... 

Regeneration of carbonyl compounds from certain derivatives. Ketones can be recovered in satisfactory yield from the phenylhydrazones, p-nitrophenyl-hydrazones, tosylhydrazoncs, oximes, and semicarhazones by reaction with 1 equivalent of (C6H,Se0)20. 2,4-Dinilrophenylhydrazones and N,N-dimethyl-hydrazones arc inert under even rather vigorous conditions. The reagent can also be used to regenerate aldehydes from oximes or tosylhydrazones. 

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. 

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