Flash vacuum pyrolysis
Hetero Diels-Alder reaction
Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
Naphtothietes and Their Application to the Synthesis of HeterocyclesThe three isomeric naphthothietes 5, 11, and 16 were prepared according to the reaction sequences shown in Schemes 1-3. The final step was in each case a flash vacuum pyrolysis (FVP) of the corresponding mercaptonaphthalenemethanol 4, 9, and 15, respectively. The thiete rings in 5 and 11 can be opened by gentle heating; the ring opening of the isomer 16 possesses a much higher activation barrier. A MNDO calculation of the ΔHf values of 5, 11, and 16 and the open isomers 5′, 11′, and 16′ provides an explanation for the different behavior. Photochemical ring opening represents a useful alternative. The reaction Schemes 4, 6, and 7 reveal the synthetic potential of the naphtho-condensed thietes. Cycloaddition reactions with CC, CO, or CN double bonds lead into the series of differently condensed thiopyrans 17, 18, 24, 25, 26, 3,1-oxathiine 19 and 1,3-thiazines 20, 21.
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