Stereoselective convergent synthesis of hydroazulenes via an intermolecular cyclopropanation/Cope rearrangement
摘要:
Rhodium(II) acetate catalyzed decomposition of vinyldiazomethane 1 to a vinylcarbenoid intermediate in the presence of oxygenated dienes led to the direct formation of hydroazulenes 7, 13, and 15-19. The 3 + 4 annulation proceeds by a tandem cyclopropanation/Cope rearrangement sequence. The cyclopropanation is highly stereoselective, favoring the formation of cis-divinylcyclopropanes. Due to the boat transition state required for the Cope rearrangement of cis-divinylcyclopropanes, the hydroazulenes are formed with predictable stereocontrol.
(ω-Ammonioalkyl)cyclopentadienides by Rhodium-Catalyzed Vinylcarbene Transfer to Semicyclic Enaminocarbonyl Compounds
作者:Gerhard Maas、Andreas Müller
DOI:10.1021/ol990546u
日期:1999.7.1
The rhodium(ll) catalyzed reaction of vinyldiazoacetate 2 with semicyclic beta-enaminocarbonyl compounds 1 provides (omega-(methylammonio)-alkyl)cyclopentadienides 3. This transformation represents a novel reaction cascade which combines carbenoid addition at a C=C bond with ring chain transformation. In some cases, products resulting from vinylcarbene insertion into the enaminic C-H bond of 1 are also isolated, These dienamines undergo subsequent isomerization to furnish betaines 3.
CANTRELL, WILLIAM R. (JR);DAVIES, HUW M. L., J. ORG. CHEM., 56,(1991) N, C. 723-727