Stepwise synthesis of selenium coronands containing an odd number of selenium atoms: 1,5,9-triselenacyclododecane and 1,5,9,13,17-pentaselenacycloeicosane

Abstract

The stepwise synthesis of two new selenium coronands containing an odd number of selenium atoms, starting from the fragments HO-(CH 2 ) 3 -Cl, HO-(CH 2 ) 3 -Br, HO-(CH 2 ) 3 -SeCN, and NCSe-(CH 2 ) 3 -SeCN, is described. The key diol containing one selenium atom, 4-selenaheptan-1,7-diol 4, was obtained in 97% yield from the reaction of 3-bromo-1-propanol 3 and the selonolate anion derived from 3-selenocyanato-1-propanol 2 by sodium metal reduction in liquid ammonia. The ditosylate 5, obtained from 4, was then treated with the bisselenolate anion derived from 1,3-bisselenocyanatopropane 6 to give the target selenium coronand, 1,5,9-triselenacyclododecane [12Se3] 7, in 96% yield. The ditosylate 5 was treated with two equivalents of the selenolate anion derived from 2 to give a second key acyclic diol 8 now containing three selenium atoms. The ditosylate 9, obtained from 8, was then treated with the bisselenolate anion derived from 6 to afford the second target coronand, 1,5,9,13,17-pentaselenacycloeicosane [20Se5] 11 in 44% yield. Keywords: selenium coronands, stepwise synthesis, macrocycles, heterocycles.