摘要:
Hydrolyses of chalcogenopyrylium dyes 1-9 give product distributions that are both heteroatom and oxygen dependent, Under anaerobic or aerobic conditions at pH 8, hydrolyses of dyes 1-4, which each contain a pyrylium ring, give 2-pentene-1,5-dione 10-13, respectively, in >90% yield from addition of hydroxide to the 2-position of the pyrylium ring followed by ring opening and tautomerization. Telluropyrylium dye 8 under anaerobic conditions over the pH range 6.9-11.0 gives a 1:1 mixture of telluropyranylidene aldehyde 14 and tris(telluropyranylidenemethyl)methane 15 derived from addition of hydroxide to the central carbon of the trimethine bridge. Under aerobic conditions, tellurophene 30(Te,Te) and trace amounts of telluropyranone 29 were also produced via oxidative mechanisms with relative yields of 30(Te,Te) increasing with pH over the pH range 6.9-11.0 and with oxygen concentration. Thiopyrylium dye 9, seleno-/thiopyrylium dye 5, selenopyrylium dye 6, and seleno-/telluropyrylium dye 7 gave hydrolysis products derived from addition of hydroxide to the 2-position of the selenopyrylium ring (thiopyrylium ring for 9) as well as to the central carbon of the trimethine backbone under both anaerobic and aerobic conditions. The resulting seleno- or thio-hemiketals ring-opened to the corresponding seleno ketones, which were then hydrolyzed to the 2-pentene-1,5-diones 11-13 from 5-7, respectively, and 11 from 9. Under aerobic conditions, some oxidation of the seleno-hemiketals from 5 and 6 were observed to give selenophenes 30(Se,S) and 30(SeSe), respectively, as well as oxidation of the telluro-hemiketal from 9 and 8 to give tellurophenes 30(Te,Se) and 30(Te,Te), repectively. Chalcogenopyranones 27-29 were also produced in modest yields in the aerobic reactions.