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Flash Vacuum Thermolysis – Synthesis and Characterization of Unstabilized Cycloalkenethiones
Author(s) -
Briard Emmanuelle,
Levillain Jocelyne,
Ripoll JeanLouis,
Dat Yves,
Marcual Albert,
Lange Catherine
Publication year - 1999
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/(sici)1099-0690(199904)1999:4<869::aid-ejoc869>3.0.co;2-o
Subject(s) - chemistry , thermal decomposition , propargyl , cycloaddition , diazomethane , yield (engineering) , sulfide , polymerization , double bond , isoprene , photochemistry , infrared spectroscopy , polymer chemistry , organic chemistry , polymer , catalysis , materials science , copolymer , metallurgy
The flash vacuum thermolysis (FVT) of cycloalkenyl allyl (or propargyl) sulfides 8 , 9 , 12 , and 13 led, as the main thermal pathway, to the conjugated cycloalkenethiones 1 , 3 , and 5 , resulting from a retro‐ene reaction. These reactive thioketones, thus obtained in ca. 70% yield, have been characterized in the gas phase by mass spectrometry, and at low temperature by IR, UV/Vis and NMR spectroscopy. The polymerization of 1 , 3 , and 5 upon warming is generally more rapid than the other attempted reactions and only the [2 + 3] dipolar cycloaddition with diazomethane led in low yield, besides polymeric materials, to isomeric 1,3‐dithiolanes 20 from cyclopentenethione 1 . The obtention of the nonconjugated cycloalkenethiones 2 and 4 , expected in the FVT of sulfides 10 and 11 , has been confirmed only by UV/Vis spectroscopy at –196 °C, due to their rapid enethiolization. In the case of the large‐ring sulfide 14 , the ( E ) geometry of the double bond favoured the competitive retro‐ene reaction yielding cyclododecene and propynethial; on the other hand, the FVT of the tricyclic gem ‐dithiol 15 , a possible precursor of cyclobutenethione ( 7 ), led to vinyl thioketene ( 18 ), obtained by thermal ring opening of 7 .