- Synthesis of (±)-Glaucine and (±)-Neospirodienone via an One-Pot Bischler-Napieralski Reaction and Oxidative Coupling by a Hypervalent Iodine Reagent
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Condensation of 3,4-dimethoxybenzeneethanamine (3d) and various benzeneacetic acids, i.e., 4a-e, via a practical and efficient one-pot Bischler-Napieralski reaction, followed by NaBH4 reduction, produced a series of 1-benzyl-1,2,3,4-tetrahydroisoquinolines, i.e., 5a-e, in satisfactory yields (Scheme 3). Oxidative coupling of the N-acyl and N-methyl derivatives 6a-e of the latter with hypervalent iodine ([IPh(CF 3COO)2]) yielded products with two different skeletons (Scheme 4). The major products from N-acyl derivatives 6a-c were (±)-N-acylneospirodienones 2a-c, while the minor was the 3,4-dihydroisoquinoline 7. (±)-Glaucine (1), however, was the major product starting from N-methyl derivative 6e. Possible reaction mechanisms for the formation of these two types of skeleton are proposed (Scheme 5).
- Huang, Wei-Jan,Singh, Om V.,Chen, Chung-Hsiung,Lee, Shoei-Sheng
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- Syntheses of lamellarins I and K by [3+2] cycloaddition of a nitrone to an alkyne
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Lamellarins I and K were obtained by a new approach based on the 1,3-dipolar cycloaddition of a nitrone to an alkyne. The key cycloaddition yields an isoxazoline which rearranges to afford the central pyrrole ring.
- Díaz,Guitián,Castedo
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p. 1164 - 1166
(2007/10/03)
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