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Thermal Rearrangements, XXII. The Propargyl‐Cope Rearrangement of meso ‐ and d,l ‐3,4‐Dimethyl‐1,5‐hexadiyne‐3,4‐diol
Author(s) -
Hopf Henning,
Hamann Uwe,
Zimmermann Gerhard,
Remmler Matthias
Publication year - 1994
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19941270526
Subject(s) - chemistry , propargyl , diastereomer , diol , ketone , pyrolysis , flash vacuum pyrolysis , catalysis , medicinal chemistry , stereochemistry , organic chemistry
The thermal behavior of meso‐ and d,1‐3,4‐dimethyl‐1,5‐hexadiyne‐3,4‐diol ( meso ‐ and d ,1–4) has been studied at 400°C in the gas phase. In a tandem reaction the diols isomerize via the bisallenes 5 first to cis ‐ and trans ‐3,4‐diacetylcyclobutene ( cis ‐ and trans ‐8) which have been detected as intermediates by 13 C‐NMR spectroscopy as well as catalytic hydrogenation to 1,2‐diacetylcyclobutane ( 9 ). Subsequently, 8 stabilizes itself by ring opening to ( E,Z )‐ and (E,E)‐3,5‐octa‐dien‐2,7‐dione (E,Z) and [(E,Z)‐ 6 ]. As a side reaction retroene cleavage of 4 to 2‐butynone ( 10 ) and methyl vinyl ketone ( 12 ) is observed. By pyrolysis of the pure diastereomers 4 it is shown that the retro‐ene process is more pronounced in the d,l than in the meso series.