79919-11-2Relevant academic research and scientific papers
Triplet photochemistry of acyl and imino cyclopropenes. a rearrangement to afford furans and pyrroles: Reaction and mechanism
Zimmerman, Howard E.,Wright, Charles W.
, p. 6603 - 6612 (2007/10/02)
Syntheses of 3-substituted 3-acylcyclopropenes and 3-benzoylcyclopropene imines were devised. A triplet rearrangement of acylcyclopropenes having C-3 aryl substitution to afford furans has been uncovered and studied with several examples. Unlike the singl
On the Mechanism of the Thermal Conversion of Cyclopropenyl-Substituted Oxazolinones to Pyridines
Padwa, Albert,Cohen, Leslie A.,Gingrich, Henry L.
, p. 1065 - 1073 (2007/10/02)
Thermolysis or photolysis of a sample of a 3-cyclopropenyl-substituted 2H-azirine produced 2-methyl-3,4,5,6-tetraphenylpyridine in high yield.The reaction can best be rationalized by a mechanism involving formation of a nitrile ylide intermediate followed by intramolecular dipolar cycloaddition to give an azabenzvalene, which subsequently rearranges to the pyridine.The thermal chemistry of a series of cyclopropenyl-substituted oxazolinones was also investigated.These oxazolinones undergo a thermally induced 1,3-dipolar cycloreversion reaction with elimination ofcarbon dioxide to generate a nitrile ylide intermediate adjacent to the cyclopropene ring.This dipole can be trapped when the thermolysis of the oxazolinone was carried out in the presence of a reactive dipolarophile.Heating a sample of 2-phenyl-4-methyl-4-(1-methyl-2,3-diphenyl-2-cyclopropen-1-yl)-Δ2-oxazolin-5-one at 150 deg C for 24 h afforded a mixture of 2,3-dimethyltriphenylpyridine (45percent), 2,4-dimethyltriphenylpyridine (20percent), and 2,5-dimethyltriphenylpyridine (35percent).The formation of these products is proposed to involve a stepwise cycloaddition of the initially generated nitrile ylide to produce a bicyclobutyl zwitterion which can either collapse to give an azabenzvalene or undergo rearrangement to a cyclobutenyl cation. This latter species closes to produce two different aza Dewar benzenes.Reorganization of the azabenzvalene and aza Dewar benzenes gives rise to the observed pyridines.Alternate mechanisms based on a concerted intramolecular cycloaddition reaction of the nitrile ylide do not account for the observed product ratios.
Photochemistry of Cyclopropene Derivatives. Synthesis and Photorearrangement of a 3-Acyl-Substituted Cyclopropene
Padwa, Albert,Akiba, Mitsuo,Chou, Chuen S.,Cohen, Leslie
, p. 183 - 191 (2007/10/02)
Two different approaches toward the synthesis of a 3-acyl-substituted 1,2,3-triphenylcyclopropene were investigated.The first involved treating triphenylcyclopropenyl perchlorate with the anion derived from 1,3-dithiane followed by hydrolysis of the resulting dithioacetal.Unfortunately, all attempts to obtain a carbonyl compound from the hydrolysis failed.The only product obtained corresponded to a 1,2-diphenyl-1,2-diacyl-substituted alkene.The second approach utilized for the synthesis involved treating 3-cyano-1,2,3-triphenylcyclopropene with methyllithium.The addition proceeded quite smoothly to give the desired 3-acetyl derivative in high yield.Irradiation of 1,2,3-triphenyl-3-acetylcyclopropene in benzene afforded a mixture of 2,3,4-triphenyl-2-cyclopentenone (60percent), 2-methyl-3,4,5-triphenylfuran (27percent), and 3-acetyl-1,2-diphenylindene (13percent).The formation of the three products obtained can be rationalized in terms of a vinylcarbene intermediate.Several different pathways are available to this species, depending on the stereochemistry about the double bond and on the conformation the oxygen atom assumes in the cis intermediate.The formation of the 2-cyclopentenone derivative provides good support for the mechanism proposed some years ago to rationalize the photochemical rearrangement of 2,5-dimethylfuran.
