Eight-Membered Rings With Two Heteroatoms 1,5

This chapter titled “Eight-membered Rings with two Heteroatoms 1,5” deals eight-membered rings with two heteroatoms in a 1,5-relationship, namely 1,5-diazocine, 1,5-oxazocine, 1,5-thiazocine, 1,5-dioxocin, 1,5-oxathiocin, and 1,5-dithiocin and covers the literature from 2007 to October 2020 (SciFindern search) reporting the chemistry of uncondensed derivatives, diheterocines fused to carbocycles and heterocycles, as well as bridged diheterocines. Among them, the 1,5-diazocine ring system is by far the largest class, based on the number of publications which constituted the 87% of the total amount of the references reported in the range of interest of CHEC IV. Thus, 1,5-diazocines were divided in three different sub-chapters: Tröger's bases and related compounds, bispidines and related compounds and other uncondensed and fused 1,5-diazocines. The main change in this chapter, with respect to CHEC-III, is related to “Experimental Structural Methods” paragraph in which it was avoided reporting the spectroscopic data (NMR, IR, UV etc.) as in the previous edition they were extensively provided and, in the latest period, they remained in the same range. Analogously, the same behavior was maintained for physical properties (solubility, melting points, chromatographic behavior, conformational issues) thanks to the coverage in “Thermodynamic Aspects” paragraph of CHEC-III, which remained substantially unchanged to-date. Actually, in this edition, the inclusion of a paragraph on biosynthesis was envisaged since Nature, in recent years, has made a significant contribution to the synthesis of secondary metabolites, especially for biologically active ones. However, no 1,5-diheterocine derivative has been reported to be synthesized by Nature. In this chapter, as happened in the previous CHEC editions, the interest in 1,5-diheterocines has been driven by the pharmacological activities shown by several derivatives or some potentially important industrial applications.