Non-Carbonyl-Stabilized Metallocarbenoids in Synthesis: The Development of a Tandem Rhodium-Catalyzed Bamford−Stevens/Thermal Aliphatic Claisen Rearrangement Sequence
A tandem rhodium-catalyzed Bamford−Stevens/Claisen rearrangement is presented. The tandem reaction uses Eschenmoser hydrazones for the in situ generation of non-carbonyl-stabilized diazo alkanes, which are presumably intercepted by Rh(II) catalysts to induce a 1,2-hydride migration. This sequence provides high levels of stereocontrol for the generation of simple acyclic (Z)-enol ethers. These enol ethers undergo either thermal or Lewis acid accelerated Claisen rearrangements to provide products of high diastereopurity. Also presented are cascade reactions, wherein a third chemical step occurs after the initial tandem sequence (i.e., Bamford−Stevens/Claisen/ene and Bamford−Stevens/Claisen/Cope).
Additional Information© 2002 American Chemical Society. Received 5 August 2002. Published online 1 October 2002. Published in print 1 October 2002. The authors wish to thank the NSF (CHE-0135056), the Dreyfus Foundation, Merck Research Laboratories, and Abbott Laboratories for financial support.
Supplemental Material - ja028020j-2_s1.pdf