HETEROCYCLES

■ A New Synthesis of Quinol-2,4-diones

Lester A. Mitscher,* George W. Clark, Toshio Suzuki, and Mohindar S. Bathala

*Department of Medicinal Chemistry, University of Kansas, 4070 Malott Hall, Lawrence, Kansas 66045-2506, U.S.A.

■ Synthesis of Homoproaporphine Related Compounds

Tetsuji Kametani,* Keiichiro Fukumoto, Fumio Satoh, Kazuo Kigasawa, and Hideo Sugi

*Pharmaceutical Institute, Tohoku University, Aobayama, Sendai 980-8578, Japan

Abstract

Catalytic hydrogenation of the enone III on platinum oxide gave a mixture of the alcohols VIa and VIb, but on palladium-charcoal afforded the ketone V, which was also obtained from VIb. Treatment of the alcohol VIa or VIb with hydrogen on platinum oxide yielded an epimeric mixture of VIa and VIb.

■ Reaction of Diketene with Lactim Ethers

Tetsuzo Kato,* Yutaka Yamamoto, and Masatsugu Kondo

*Pharmaceutical Institute, Tohoku University, Aobayama, Sendai 980-8578, Japan

Abstract

Reaction of 2-methoxy-1-pyrroline (Ia) with diketene without solvent affords 7-hydroxy-2,3-dihydro-1H,5H-indolizin-5-one (IIa) and 8a-methoxy-2-methylene-3,4,6,7,8,8a-hexahydro-2H-pyrrolo[2,1-b]-1,3-oxazin-4-one (IIIa) which, on treatment with sodium ethoxide, is transformed to 8a-methoxy-2-methyl-6,7,8,8a-tetrahydro-4H-pyrrolo[2,1-b]-1,3-oxazin-4-one (IVa).
Similarly, 2-methoxy-3,4,5,6-tetrahydropyridine (Ib) gives 2-hydroxy-6,7,8,9-tetrahydro-4H-quinalizin-4-one (IIb) and 9a-methoxy-2-methyl-7,8,9,9a-tetrahydro-4H,6H-pyrido[2,1-b]-1,3-oxazin-4-one (IVb).
Reaction of 2-methoxy-4,5,6,7-tetrahydro-3H-azepine (Ic) gives 10a-methoxy-2-methy1-6,7,8,9,10,10a-hexahydro-4H-azepino[2,1-b]-1,3-oxazin-4-one (IVc).

■ Synthesis of Benzazepine Alkaloids and Related Compounds

Tetsuji Kametani* and Keiichiro Fukumoto

*Pharmaceutical Institute, Tohoku University, Aobayama, Sendai 980-8578, Japan

Abstract

The various total synthesis and synthetic approaches to the isopavine, cephalotaxine and rheadan alkaloids, which have a 1,2,4,5-tetrahydro-3H-benz[d] azepine system as the main framework, are described. This review also summarises the synthetic reactions of benz[d]azepine.

■ Application of Lead Tetraacetate Oxidation to the Synthesis of Isoquinoline Alkaloids

Bunsuke Umezawa* and Osamu Hoshino

*Faculty of Pharmaceutical Sciences, Science University of Tokyo, 2641 Yamazaki, Noda, Chiba 278-8510, Japan

Abstract

A variety of 7- or 6-tetrahydroisoquinolinols are readily oxidized with lead tetraacetate in acetic acid or methylene chloride to give p-quinol acetates or 4-acetates, whose acid treatment has produced (±)-aporphines, (±)-homoaporphines, (±)-homomorphinandienones, and (±)-homoproaporphines or (±)-isopavines, respectively.

■ Applications of Free Radical Reactions in Heterocyclic Chemistry

Karl Heusler*

*Pharmaceuticals Division, Research Department, Ciba-Geigy Limited, CH-4002 Basel, Switzerland

Abstract

Organic oxygen and nitrogen free radicals are easily generated and can be used for the preparation of heterocyclic systems. In the present review, the application of such intramolecular as well as intermolecular radical reactions to the synthesis of various polycyclic compounds is discussed.