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Synthesis 2012; 44(14): 2185-2194
DOI: 10.1055/s-0031-1291041
DOI: 10.1055/s-0031-1291041
special topic
Lewis Acid Catalyzed Benzylic C–H Bond Functionalization of Azaarenes; Addition to Imines and Enones
Further Information
Publication History
Received: 06 April 2012
Accepted: 10 April 2012
Publication Date:
14 May 2012 (online)
Abstract
Lewis acid catalyzed benzylic C–H bond functionalization of alkyl-substituted azaarenes is described. The addition to N-tosyl imines proceeded under solvent-free conditions using various Lewis acids. Cu(OTf)2 was the best Lewis acid, and 1,2-addition proceeded at 60–120 °C, giving products in 23–92% yield. On the other hand, strongly Lewis acidic rare-earth metal triflates, Sc(OTf)3 and Y(OTf)3, were essential to promote the 1,4-addition of alkyl-substituted azaarenes to enones, and products were obtained in 60–96% yield.
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References
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For selected general reviews on C–H bond functionalization, see:
For selected leading examples involving C–C bond formation, see:
Lewis acid catalyzed benzylic C–H functionalization of 2-methyl azaarenes. For reactions of aldimines with Sc(OTf)3, see:
With Cu(OTf)2, see:
For related Brønsted acid catalyzed addition to activated carbonyl compounds, see:
For Sc(OTf)3, BF3·Et2O, and PtCl4 catalyzed intramolecular coupling of C(sp3)-H bonds and electron-deficient alkenes via 1,5-hydride transfer, see:
For Sc(OTf)3 and SnCl4 catalyzed intramolecular C–H functionalization via 1,5-hydride transfer and 1,6-hydride transfer, see:
For Gd(OTf)3, Mg(OTf)2, and Ni(ClO4)2 catalyzed intramolecular (asymmetric) reactions with electron-deficient alkenes via 1,5-hydride transfer, see:
For Lewis acid assisted functionalization under Ni(0) catalysis, see:
For examples using rare-earth metal triflates, see:
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