The photochemical reaction between aromatic nitriles and allylsilane
摘要:
The results obtained from the irradiation of aromatic nitriles and allyltrimethylsilane (ATMS) depend on the redox parameters of these molecules and their singlet energies. The reaction between 1-naphthalenecarbonitrile (NN) and ATMS in apolar solvents leads to [2 + 2] cycloaddition at positions 1 and 2 (via the exciplex); in polar solvents, electron transfer becomes a possibility, and loss of the trimethylsilyl cation followed by allylation of NN at positions 2 and 4 is also observed. When naphthalene-1,4-dicarbonitrile (NDN) is used, electron-transfer-initiated allylation (both addition and cyano group substitution) is the main pathway, but in apolar solvents cycloaddition at positions 4a and 5 occurs as a minor pathway. The reaction with benzene-1,2,4,5-tetracarbonitrile (BTN) gives substitution of an allyl for a cyano group as the only process. Finally, with both NDN and BTN and a high ATMS concentration in apolar solvents, the reaction pathway changes to photosensitized [2 + 2] dimerization of ATMS, proposed to occur via a terplex. Rationalizations for the observed reactions (including regiochemistry of addition and cycloaddition and nature of the intermediates) are offered.
The photochemical reaction between aromatic nitriles and allylsilane
摘要:
The results obtained from the irradiation of aromatic nitriles and allyltrimethylsilane (ATMS) depend on the redox parameters of these molecules and their singlet energies. The reaction between 1-naphthalenecarbonitrile (NN) and ATMS in apolar solvents leads to [2 + 2] cycloaddition at positions 1 and 2 (via the exciplex); in polar solvents, electron transfer becomes a possibility, and loss of the trimethylsilyl cation followed by allylation of NN at positions 2 and 4 is also observed. When naphthalene-1,4-dicarbonitrile (NDN) is used, electron-transfer-initiated allylation (both addition and cyano group substitution) is the main pathway, but in apolar solvents cycloaddition at positions 4a and 5 occurs as a minor pathway. The reaction with benzene-1,2,4,5-tetracarbonitrile (BTN) gives substitution of an allyl for a cyano group as the only process. Finally, with both NDN and BTN and a high ATMS concentration in apolar solvents, the reaction pathway changes to photosensitized [2 + 2] dimerization of ATMS, proposed to occur via a terplex. Rationalizations for the observed reactions (including regiochemistry of addition and cycloaddition and nature of the intermediates) are offered.
The photochemical reaction between aromatic nitriles and allylsilane
作者:M. Mella、E. Fasani、A. Albini
DOI:10.1021/jo00049a031
日期:1992.11
The results obtained from the irradiation of aromatic nitriles and allyltrimethylsilane (ATMS) depend on the redox parameters of these molecules and their singlet energies. The reaction between 1-naphthalenecarbonitrile (NN) and ATMS in apolar solvents leads to [2 + 2] cycloaddition at positions 1 and 2 (via the exciplex); in polar solvents, electron transfer becomes a possibility, and loss of the trimethylsilyl cation followed by allylation of NN at positions 2 and 4 is also observed. When naphthalene-1,4-dicarbonitrile (NDN) is used, electron-transfer-initiated allylation (both addition and cyano group substitution) is the main pathway, but in apolar solvents cycloaddition at positions 4a and 5 occurs as a minor pathway. The reaction with benzene-1,2,4,5-tetracarbonitrile (BTN) gives substitution of an allyl for a cyano group as the only process. Finally, with both NDN and BTN and a high ATMS concentration in apolar solvents, the reaction pathway changes to photosensitized [2 + 2] dimerization of ATMS, proposed to occur via a terplex. Rationalizations for the observed reactions (including regiochemistry of addition and cycloaddition and nature of the intermediates) are offered.