Premium
Synthesis of Polyalkylphenyl Prop‐2‐ynoates and Their Flash Vacuum Pyrolysis to Polyalkylcyclohepta[ b ]furan‐2(2 H )‐ones
Author(s) -
Nagel Matthias,
Hansen HansJürgen
Publication year - 2000
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/(sici)1522-2675(20000510)83:5<1022::aid-hlca1022>3.0.co;2-y
Subject(s) - chemistry , furan , flash vacuum pyrolysis , aryl , lithium (medication) , toluene , sodium , medicinal chemistry , ring (chemistry) , yield (engineering) , pyrolysis , organic chemistry , medicine , alkyl , materials science , metallurgy , endocrinology
A new method for the smooth and highly efficient preparation of polyalkylated aryl propiolates has been developed. It is based on the formation of the corresponding aryl carbonochloridates ( cf. Scheme 1 and Table 1 ) that react with sodium (or lithium) propiolate in THF at 25 – 65°, with intermediate generation of the mixed anhydrides of the arylcarbonic acids and prop‐2‐ynoic acid, which then decompose almost quantitatively into CO 2 and the aryl propiolates ( cf. Scheme 11 ). This procedure is superior to the transformation of propynoic acid into its difficult‐to‐handle acid chloride, which is then reacted with sodium (or lithium) arenolates. A number of the polyalkylated aryl propiolates were subjected to flash vacuum pyrolysis (FVP) at 600 – 650° and 10 −2 Torr which led to the formation of the corresponding cyclohepta[ b ]furan‐2(2 H )‐ones in average yields of 25 – 45% ( cf. Scheme 14 ). It has further been found in pilot experiments that the polyalkylated cyclohepta[ b ]furan‐2(2 H )‐ones react with 1‐(pyrrolidin‐1‐yl)cyclohexene in toluene at 120 – 130° to yield the corresponding 1,2,3,4‐tetrahydrobenz[ a ]azulenes, which become, with the growing number of Me groups at the seven‐membered ring, more and more sensitive to oxidative destruction by air ( cf. Scheme 15 ).