Phenylcyclopropanes, photolysis

Several studies of the application of the photoextrusion of S02 have been conducted in substituted analogs of the parent compounds above. For example, the photolysis of 2-phenylthietane 1,1-dioxides (34), in dichloromethane or methanol, at 254 nm affords the expected phenylcyclopropanes in almost quantitative yields68. The 2-phenyl substituent... 

A second reaction of this type is of interest because it reveals the nature of the diradical produced. Here we have l-benzoyl-2-aryl-3-phenylcyclopropanes. The aryl groups in the study were p-cyanophenyl, anisyl and phenyl50. It was observed that the 2,3-trans,trans isomer, in which the benzoyl group was trans to both aryl groups, on photolysis afforded the cis-trans isomers in which the substituted aryl group was now cis to benzoyl. One might... 

Although pyrolysis of several phenyl-substituted cyclopropanes results in extrusion of phenyl-carbene, which undergoes addition to C-C double bonds and forms phenylcyclopropanes under the experimental conditions employed, the overall efficiency of the process is generally too low to make it an attractive method for synthesis on a preparative scale. Thus, phenylcarbene, generated by photolysis of trans-l,2-diphenylcyclopropane or 1,2,3-triphenylcyclo-propane, forms 2-ethyl-2-methyl-1-phenylcyclopropane in only 6% yield as a mixture of isomers when the reaetions are carried out in 2-methylbut-l-ene. ... 

A mixture of 1-aryl-l-chlorodiazirine and an alkene in hexane sonicated with ultrasound (Fisher Scientific Solid State Ultrasound FS-9) at 40 °C for two hours afforded 1-aryl-l-chlorocyclo-propanes with yields similar to those obtained by photolysis. Electrophilic as well as nucleophilic alkenes were used. Photolytic, thermal or ultrasonic decomposition of 3-chloro-3-phenyl-3//-diazirine in 2-vinylpyridine did not give the corresponding 1-chloro-l-phenylcyclopropane derivative (see Section 1.2.1.3.1.2.2.1). 

Diazo derivatives are not the exclusive precursors of carbenes. The photolysis of 1-di-ethoxyphosphoryl-l,2,2-triphenyloxirane (4) in the presence of 2-methylpropene gave 1-diethoxyphosphoryl-2,2-dimethyl-l-phenylcyclopropane (5) in 45% yield. For comparison, cyclopropane 5 was obtained in 86% yield starting from the corresponding diazo derivative. ... 

Hence the photolysis of the y-phenyl substituted lactone (5-phenyldihydro-2(3/f)-furanone 1) gave a 36% yield of phenylcyclopropane (2), but the corresponding a- and )S-substituted lactones gave negligible yields. 

Finally, photolysis of l-methyl-5-phenyl-4,5-dihydro-l//-pyrazole gave a mixture of stereoisomers of 1 -methylazenyl-2-phenylcyclopropane (16) which can be converted back to the starting material thermally. The same reaction is observed for the 1,3-dimethyl derivative, but if the iV-methyl substituent is lacking, ring-opening reactions predominate. ... 

Methyl-1-phenylcyclopropane (1) was obtained in 33% yield when phenylcyclopropane in tetrahydrofuran was reacted with trimethylsilylmethylpotassium and then with iodo-methane. Photon-induced hydrogen abstraction promoted formation of 7b-phenyl-la,7b-di-hydro-l/f-cyclopropa[a]naphthalen-3(2/f)-one (2) from photolysis of /ra v-l-phenyl-2-(2-oxo-... 

Photolysis of 6-phenyl- and 6,7-diphenyl-4,5,6-triazaspiro[2.4]hept-4-ene la and lb dissolved in dichloromethane with filtered light (A > 295 nm) from a mercury lamp resulted in nitrogen expulsion and formation of the corresponding phenyl-substituted l-azaspiro[2.2]pentanes A similar reaction occurred when methyl 4,5-dihydro-l-(l-phenylcyclo-propyl)-l,2,3-triazole-4-carboxylate (3), obtained by treating methyl acrylate with 1-azido-l-phenylcyclopropane, was refluxed in toluene. 

Another solvent dependent intermolecular addition reaction involving phenylcyclopropane (64) as the electron donor was recently reported. Irradiation of N-methylphthahmide 42 in acetonitrile in the presence of 64 afforded a 1 1 mixture of isomeric spiro-tetrahydrofuranyl lactams 65 in 22% yield. An intramolecular version of this PET reaction has also been described."" When the photolysis was performed in methanol, solvent-incorporated addition to produce 66 took place (Scheme 23). 

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