Endocyclic enecarbamates

The preparation of 3-pyrroline was recently reported in Organic Syntheses The protected form, N-Boc-3-pyrroline, has been used effectively in Heck arylations for the preparation of various 4-aryl endocyclic enecarbamates. It has also been used in the preparation of regioisomeric 3-hydroxyisoxazolinyl prolines which are medicinally active. The catalytic asymmetric hydroformylation of N-Boc-pyrroline has been investigated. N-Boc-pyrroline has also been utilized in the synthesis of various antibacterial compounds. ... 

Dehydration. Endocyclic enecarbamates are prepared from the corresponding lactams via reduction and subsequent dehydration with TFAA-2,6-lutidine. ... 

The [2+2] cycloaddition reaction of 4-aryl endocyclic enecarbamates 194 with 2-chloroethyIketene, generated in situ, affords exclusively cndo-(2-chloroethyl)-cyclobutanones 195. ... 

The endoselectivity in the formation of 195 is significantly higher than that observed for the reaction of the unsubstituted endocyclic enecarbamates with mono substituted ketenes. When alkylketenes are used in the reaction of substituted endocyclic enecarbamates high stereoselectivity is also observed... 

We reported our first results with the Heck-Matsuda reaction in the late 1990s for the arylation of chiral, nonracemic, endocyclic enecarbamates 9 to produce the aryl pyrroUdines 8. These interesting intermediates were further applied in the total synthesis of several fully substituted A -heterocycles with pharmacologically active compounds such as the antibiotic and hypertensive pyrrolidine alkaloid codonopsinine 6, and the antitrypanosomal Schramm s C-azanucleoside 7 (Scheme 4). ... 

SCHEME 4 Heck-Matsuda reaction of endocyclic enecarbamates. 

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