1467-01-2Relevant articles and documents
Photoadditions of Ethers, Thioethers, and Amines to 9,10-Dicyanoanthracene by Electron Transfer Pathways
Hasegawa, Eietsu,Brumfield, Martha A.,Mariano, Patrick S.,Yoon, Ung-Chan
, p. 5435 - 5442 (2007/10/02)
Studies were conducted to explore single electron transfer (SET) induced photoaddition reactions of 9,10-dicyanoanthracene (DCA) with a variety of n-electron donors including silicon-containing substrates (EtOCH2TMS, EtSCH2TMS, and Et2NCH2TMS).Photoadditions of EtOCH2TMS and EtSCH2TMS to DCA in MeCN occur in high yields to produce 10-substituted 9,10-dicyano-9,10-dihydroanthracenes in which the anthracenyl unit is bonded to the ether or thioether in place of the TMS substituent.The photoadducts undergo base-induced dehydrocyanation and oxidation to generate the respective 10-substituted 9-cyanoanthracenes and 10-substituted 10-cyano-9-anthrones.Photoaddition of Et2NCH2TMS to DCA in MeCN produces the corresponding dihydroanthracene adduct, which spontaneously dehydrocyanates under the reaction conditions to yield the coresponding 10-substituted 9-cyanoanthracene.This process is inefficient as compared to the O and S analogues; other products from this reaction include 9-cyano-10-aminoanthracene, 9-cyanoanthracene, and 9-cyano-10-methylanthracene.The latter product is shown to arise by secondary photoreaction of the Et2NCH2TMS-DCA anthracene adduct.Mechanism for these photoadditions involving SET from the n donors to DCAS1 followed by selective desilylation of the intermediate cation radicals and radical coupling are proposed.In contrast, photoadditions of Et2O and THF occur in high yield while that of Et2NMe to DCA is inefficient.These processes follow sequential electron-transfer-deprotonation pathways.Finally, the α-amino radical, Et2NCH2, an intermediate in the DCA + Et2NCH2TMS photoreaction, is trapped by added cyclohex-2-en-1-one and its 4,4-dimethyl analogue via routes involving conjugate radical addition.Adduct formation between these enones and Et2NCH2TMS represents a novel method for initiating radical addition processes by use of SET photosensitization.
