Synthesis of (-)-Piperitylmagnolol Featuring ortho-Selective Deiodination and Pd-Catalyzed Allylation.

A 1,4-addition strategy using an enone and a copper reagent was studied for the synthesis of (-)-piperitylmagnolol. A MOM-protected biphenol copper reagent was added to BF3·OEt2-activated 4-isopropylcyclohexenone, whereas 1,4-addition of protected monophenol reagents possessing an allyl group was found to be unsuccessful. The allyl group was later attached to the p-,p'-diiodo-biphenol ring by Pd-catalyzed coupling with allylborate. The aforementioned iodide was synthesized using a new method for ortho-selective deiodination of o-,p-diiodophenols.

Activation of Marginally Reactive Boron Enolates by MeLi for the Formation of Enol Phosphates and Synthesis of the Δ(9)-THC Intermediate.

The addition of MeLi to boron enolates produced by the 1,4-addition of Ar2Cu(CN)Li2 to BF3·OEt2-activated enones was followed by the reaction with ClP(O)(OEt)2 to afford the corresponding enol phosphates in moderate to good yields. The scope of this method was examined with sterically hindered or electronically biased enones and/or reagents. This activation of boron enolates was successfully applied to the synthesis of the methyl ether of Δ(9)-tetrahydrocannabinol.

Synthesis of trans-2,6-disubstituted cyclohexanones through allylic substitution.

trans-2,6-Disubstituted cyclohexanones were synthesized with high regio- and stereoselectivity by allylic substitution followed by ozonolysis. Both alkyl and aryl groups were successfully installed to the cyclohexane ring. The stereochemistry of the SN2' products was determined to be controlled by the pre-existing chirality on the ring. The present method is highlighted by the synthesis of enantiomerically enriched cyclohexanones.