Tosylhydrazone salts, photolysis

As shown in Table 1, however, the product distribution depends on the method of carbene generation. Whereas thermolysis of either tosylhydrazone salt (7) or methylethyldiazirine (8) affords essentially the same product distribution (in which 95% of the products are the 2-butenes), photolysis of diazirine 8 is quite different. 

Product analysis of the products of photolysis or thermolysis of conformationally biased tosylhydrazone salts (72) showed that a bystander equatorial Me group promotes a geminal H-shift several times more effectively than does an axial Me.78 The observation that the primary isotope effect for axial deuterium migration was 1.5 times that for equatorial migration in (72 R1 = R2 = D, R3 = Me) invalidates the common assumption that these isotope effects are equal. 

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). 

Thus photolysis of the tosylhydrazone sodium salt of 5//-dibenzo[a,c]cyclohepten-5-one (14) at — 60 °C in the presence of cyclopentadiene or furan with tetrahydrofuran as cosolvent gave the cyclopropene Diels-Alder adducts 17 and 18 in 73 and 47% yields, respectively. If the photolysis was stopped shortly after all the tosylhydrazone salt had decomposed, adduct 17 was the only isomer found in the cyclopentadiene reaction. In the formation of the furan adduct 18, the reaction was not so clean and a number of unidentified products were also formed. Unfortunately, adduct 18 is thermally unstable at the temperature necessary for thermal formation of carbene 15. No trace of adduct 18 was detected when the arylcarbene 19 was generated directly from its tosylhydrazone salt in the presence of furan. ... 

The carbene generated by photolysis of the tosylhydrazone salt (117) adds to the intramolecular triple bond to provide the second example of a bicyclo[4,l,0]hepta-l(7),2,4-triene, which can be trapped by butadiene to give the norcaradiene (118) (Scheme H). " ... 

An interesting intramolecular reaction is thermolysis or photolysis of the tosylhydrazone salt (102) (Scheme 12). By thermolysis of (103a) and (103b), (105a) was obtained in 45% yield and exo- and endo- l05h) were obtained in... 

Thermolysis and/or photolysis of tosylhydrazone salts, accessible by condensation of p-toluene-sulfonyl-hydrazine with aldehydes or ketone, gives rise to elimination of the sulfinate salts and forms the intermediate diazo compound (Scheme 18). Generation of free carbenes by this method is sometimes in doubt and, as a consequence, this method is not included in this chapter except when generation of a carbene from the diazirine or diazo compound is not available. 

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. 

Photolysis of the tosylhydrazone sodium salt (94) in diglyme gave, as the major product, 1,3-diene (95) by [l,2]-vinyl shift in the intermediate carbene. Vinyl migration occurs with retention of configuration and is postulated to occur in the singlet manifold. 

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... 

Pyridazines were obtained also by photolysis of 1-phenyl-l-vinyl azide in the presence of iron pentacarbonyl (3,6-di-phenylpyridazine was obtained in 1.1% yield) (78HCA589) or by thermal decomposition of an allenic hydrazonate (81JA7011). Acetylenic hydrazides can be transformed into pyridazines [84BSF(2)129], and thermal cyclization of dialkali metal salts of cu-hydroxyketone tosylhydrazones afforded pyridazines in moderate yield (85TL655). Propionyl phenylhydrazine, after reaction with 4-bromobutyronitrile, converts into a pyridazine (87SC1253). 

Mechanistic information on the photolytic Bamford-Stevens reaction is provided by the successful isolation of a diazo hydrocarbon as a reaction intermediate from the direct photolysis of a tosylhydrazone sodium salt (90 Scheme 10). This study also clarifies that the carbene derived thermally and that derived photolytically behave differently with respect to the stereoselectivity of the 1,2-hydrogen shift that produces the alkene. 

Free carbene 429 generated by photolysis or thermolysis of the diazo compound cyclizes into the sulfonium ylide, which undergoes a thia-Stevens rearrangement to 430 in 19% yield. The same result was obtained using the corresponding p-tosylhydrazone sodium salt as a carbene precursor (83JA6096). Rh(II)-catalyzed decomposition of sulfur-containing diazo... 

In situ generation of diazoalkenes can be performed using alkali-metal salts of a,j -unsaturated tosylhydrazones. An early intramolecular application of this method was the photolysis of the sodium hydrazonide 22 to give the sesquiterpene thujopsen (23, 4%). However, the major product formed was the cyclopropene 24, generated via an intramolecular insertion reaction. ... 

Photolyses of salts of tosylhydrazones give complex mixtures of products. Nonetheless, the thermolysis or photolysis of the sodium salts of tosylhydrazones is a longstanding route to cyclopropenes, although yields are rarely very high. Some more recent applications of the method are given. In particular, the l,6-dimethyl-1,6-diphenylspiro[2.5]oct-l-ene was formed as a trans/eix mixture in 95% yield. 

Xanthenyliumsodium (from sodamide and xanthene) reacts with aziridines to give a mixture of 9-mono- (271) or 9,9-di-substituted xanthenes (272).Addition of perchloric acid to unsymmetric allenes such as the 9-xanthylidene derivative (273) (prepared by a new route from 9,9-dichloroxanthene and an alkene) gave a red xanthylium salt (274), which was converted into a colourless spiro-indene (275) on heating.Full details have now been published of the properties and of the reactions of 9-diazoxanthene (276) and 9-xanthylidene (278) with methyl acrylate, substituted styrenes, several ketones, and alkyl-benzenes. The kinetics of the reaction with styrenes were studied and the conversion of (276) into (278) was achieved by photolysis of the tosylhydrazone (277) at —25 °C. 

Ratio of cyclopentadiene The formation of bicyclopentene is formally an electro-cyclic reaction like that which converts the benzene system to a Dewar benzene [47], and the formation of 3 is crossed cycloaddition like that which converts benzene to benzvalene [48]. Stmctural derivatives of 3 were known prior to the isolation of the parent Masamune prepared 1,5-diphenyl tricyclo[2.1.0.0 Jpentan-3-one by photolysis of a diazocyclopropenyl ketone [49] (X-ray analysis of a derivative confirmed the structure in the face of skepticism [50,51] and Closs and Larrabee prepared 2,4-dimethyltricyclo[2.1.0.0 ]pentane [52] by heating the sodium salt of a cyclobutenyl tosylhydrazone both kinds of reactions are known to generate carbenes or carbe-noids, and presumably involve insertion of a carbene-type carbon into a carbon-carbon double bond ... 

Carbene formation during vacuum-UV photolysis (7.6 eV) and radiolysis of cyclooctane by unimolecular H2 elimination from a single carbon atom (1,1-elimination) was shown to be the main reaction channel of excited cyclooctane (equation 6)". The carbene 6 is formed with an efficiency close to 100% in the long-wavelength photolysis of the sodium salt of the p-tosylhydrazone 7 as well as in the vacuum-UV photolysis and radiolysis of cyclooctane. This was deduced from the similar product distribution of both reactions to give cyclooctene (8), bicydo[3.3.0]octane (9) and bicyclo[5.1.0]octane (10) ... 

Bu Li at - 30 °C, followed by treatment with Mel. A diallyl sulphide behaves similarly in that one of the two S-substituents is lithiated, and this centre is the point at which the y-carbon of the other S-substituent is attached in the product. Compounds (67)—(69) are formed in approximately equal amounts by the photolysis of the /S-alkylthioalkyl-carbene derived from 3-crotyl-3-methylbutyrophenone tosylhydrazone sodium salt. An a-allylthioalkyl-carbene (70) behaves differently on irradiation at - 70 °C, giving an intermediate (71) which rearranges, without the need for irradiation, to give the violet thione (72) this last step is the first... 

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. 

Phenyl(trimethylsilyl)carbene (21) has been generated from phenyl(trimethylsilyl)diazo-methane (20) by gas-phase pyrolysis as well as by thermolysis or photolysis " in solution, by flash thermolysis of the tosylhydrazone hthium salt 180 , and by pyrolysis... 

This puts on a quantitative basis the notion that this aromatic carbene, made by photolysis of the sodium salt of the corresponding tosylhydrazone, is in fact nucleophilic. 

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