Electron-transfer-induced photocyclization reactions of arene-iminium salt systems. Effects of cation diradical deprotonation and desilylation on the nature and efficiencies of reaction pathways followed

Journal Article · Wed Apr 29 04:00:00 EDT 1987 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00243a029· OSTI ID:6800232

Lan, A J.Y.; Heuckeroth, R O; Mariano, P S

Photocyclization reactions of the N-xylyl-1-pyrrolinium perchlorates 3-6, induced by excited-state electron transfer, have been explored with the intent of uncovering mechanistic details and developing synthetic applications. Both of the silicon-substituted salts 4 and 6 undergo photocyclization to produce the respective benzoindolizidine products, 30 and 13, exclusively via mechanisms involving sequential electron transfer-desilylation. On the other hand, the non-silicon-containing 2-phenyl-1-pyrrolinium perchlorate 5 undergoes conversion to both the indolizidine 13 and 2-phenyl-1-pyrroline (10) upon irradiation. Photofragmentation generating 10 is proposed to arise by cleavage of the intermediate diradical cation 14, which occurs in competition with deprotonation and 1,6-diradical coupling to form 13. Finally, the benzopyrrolizidines 22 and 23 are produced when the 2-methyl-N-xylyl- and 2-methyl-N-benzylpyrrolinium perchlorates 3 and 21 are irradiated. Deuterium labeling studies have shown that these photocyclization reactions proceed through diradical cation coupling processes. The features of these photochemical processes whose chemical outcomes are dependent upon the nature of reaction pathways available to cation diradical intermediates are discussed. Finally, the photoinduced, diradical cyclization methodology for transformation of the silicon-containing N-xylylpyrrolinium perchlorates 4 and 6 has been compared to the alternative dipolar pathway promoted by fluoride-induced desilylation. The indolizidines 30 and 13 are formed when these salts are treated with cesium fluoride at high temperature. However, the yields are much lower than those observed for the photocyclization processes.

• Research Organization: Univ. of Maryland, College Park
• OSTI ID: 6800232
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 109:9; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400500* -- Photochemistry
AROMATICS
CATIONS
CHARGED PARTICLES
CHEMICAL REACTION YIELD
CHEMICAL REACTIONS
CHEMISTRY
DATA
DEHYDROCYCLIZATION
ELECTRON TRANSFER
ENERGY LEVELS
EXCITED STATES
EXPERIMENTAL DATA
IMINES
INFORMATION
IONS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOCHEMISTRY
RADICALS
REACTION INTERMEDIATES
YIELDS