Chapter 52 - Compounds with Larger Heterocyclic Rings: Seven-Membered Ring Compounds with Two or More Different Elements in the Ring

Abstract

Publisher Summary This chapter describes the seven-membered ring compounds with two or more different elements in the ring. General methods of synthesis are discussed for compounds with rings containing oxygen and nitrogen. These include the oxazepines, such as 1,2-oxazepines, 1,3-oxazepines, 1,4-oxazepines, and oxadiazepines, which are important intermediates in the asymmetric synthesis of α-amino acids. Compounds with rings containing oxygen and sulfur, such as 1,3-oxathiepan-2-one and 2,3-diphenyl-5,6-dihydro-7H-1,4-oxathiepin have attracted little attention and references to them are scattered. Compounds with rings containing nitrogen and sulfur include the thiazepines, such as 1,2- and 1,3-thiazepines, 1,4-thiazepines, 1,5-thiazepines, and benzothiazepines. The preparation and reactions of dibenzo[b,f]-1,4-thiazepines are similar to those of their 5-oxa analogues. Many 3-substituted 1,2,4-benzothiadiazepine 1,1-dioxides are prepared by treating 2-benzoyl-4-chlorobenzenesulfonyl chloride with amidines, guanidine or S-alkylisothioureas and cyclizing the products with an acid catalyst. Dithiazepines such as Cystamine, are oxidized by diamino oxidases of plant or animal origin to 6,7-dihydro-3H-1,2,5-dithiazepine (cystaldimine). Compounds with rings containing nitrogen and selenium are prepared by heating the zinc salt of 2-aminobenzeneselenol in ethanolic hydrochloric acid with α,β-unsaturated ketones. 2,2,4-trimethyl-2,3-dihydro-l,5-benzoselenazepine and analogues are formed. Compounds having a seven-membered ring with three different heteroatoms, such as nitrogen, oxygen and sulfur occur mainly as “accidentals.”