BF3-promoted synthesis of diarylhexahydrobenzo[f]isoquinoline.

An easy and straightforward synthesis of 6,10b-diarylhexahydrobenzo[f]isoquinoline by the repeated treatment of boron trifluoride etherate (BF(3) x OEt(2)) is reported. The overall transformation from 4-arylpiperidin-3-one to benzo[f]isoquinoline proceeds via ring contraction, chain elongation, and intramolecular electrophilic cyclization in moderate yields. It presents a novel rearrangement reaction catalyzed by boron trifluoride etherate and broadens the scope of application.

Efficient synthesis of fused bicyclic glutarimides. Its application to (+/-)-alloyohimbane and louisianin D.

[reaction: see text] The reaction of alpha-sulfonyl acetamide 1 with various cyclic unsaturated esters 2 to fused bicyclic glutarimides is reported. Syntheses of (+/-)-alloyohimbane (4) and louisianin D (5) have been accomplished.

Regioselective reduction of 3-sulfonyl glutarimides to 3,4-dihydro-5-sulfonylpyridin-2-ones. Formal synthesis of the indolizidine 8a-epi-dendroprimine.

Sodium borohydride regioselectively reduced various 3-sulfonyl glutarimides 1 to hydroxy piperidones 2, which were further dehydrated to 3,4-dihydro-5-sulfonylpyridin-2-ones 3 in the presence of boron trifluoride. Formal synthesis of 8a-epi-dendroprimine (4) possessing an indolizidine ring system has been accomplished via intramolecular radical cyclization of cyclic vinyl sulfone 5.