Nine- and Ten-Membered Heterocycles

Another reaction that is relevant to the mechanism of the formation of the alkaloid erysodienone in vitro is the K3[Fe(CN)6]-induced para-para oxidative coupling of the phenol (13) to the azoninone derivative (14). ° Oxymercuration-demercuration [by Hg(OAc)2 and then NaBH4] of the cyclic lactam (15) resulted in the regio- and stereo-specific transannular formation of (16). The conformation of (15) is represented by (17), in which there is no steric crowding by the methyl group. The ring is believed to be responsible for the course of the reaction. 

Isomerization of the pyridazino-azonine derivative (18) to the c -isomer in boiling benzene probably reflects a release of skeletal strain and contrasts with the cis - trans isomerization found previously for the potassium salts of the 

Topalova, Nauchn. Osn. Pererab. Nefti Gaza Neftekhim., Tezisy Doki, Vses. Konf., 1911, 191 (Chem. Abstr., 1980, 92, 58 482). 

The condensation of (21) with methanal gave (22) as the isolated crystalline product, i.e. a dimer of the expected compound (23). However, n.m.r. showed that, in CHCI3, dissociation of (22) to (23) does occur, but that, in addition, the ion (24) is present in the equilibrium. The intermediate that is believed to be responsible for these interconversions is (25). 

Cervinka, V. Dudek, Z. Stihel, and J. Zikmund, Collect. Czech. Chem. Commun., 1979,44, 2843 Chem. Abstr., 1980, 92, 128 879). 

A new method for the synthesis of medium-ring lactones from cyclic sulphide precursors has been reported. The thiolo-lactone (31) rearranges 

Heidelberger, A. Guggisberg, E. Stephanou, and M. Hesse, Helv. Chim. Acta, 1981, 64,399. 

A four-carbon cyclo-enlargement of the cyclic thioketal (33) by a [4 + 2] cycloaddition with dichloroketen yields the 1,4-dithia-derivative (34). This is a potentially valuable route to many multifunctional dithia-macrocyclic systems. 

Treatment of Br(CH2) Br with NaaS under heterogeneous conditions yields the appropriate thiacycloalkane. Similarly, the oxidative cyclization of the dithiol HS(CH2) X(CH2) SH (X = O, CH2, or S) with iodine yields the corresponding medium-ring disulphide. A general synthesis of mediumring and macrocyclic disulphides and a variety of dithia-crown ethers has been devised, using caesium dithiolates as starting materials [reaction (1)].  

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CuI/DMEDA-catalyzed coupling of -lactam 152 with 2-halophenylamines, 2-halobenzylamines and related aryl halides worked at 1 lO C, yielding aryl amides 153, which underwent ring expansion under the assistance of acetic acid to produce lactams 154. This method was proven useful for assembling seven-, eight-, nine-, and ten-membered heterocycles (Scheme 51) [91]. 

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