Summary.
5-Trifluoroacetyl-3,4-dihydro-2H-pyran react readily with many nucleophiles such as amines and Grignard reagents to give the rign opened products NuCH*CR 1 R 2 (R 1: (CH2)3OH, R 2:CF3CO). The compound with Nu=Et2N is unstable; it rearranges to 1-hydroxyl-1-trifluoromethyl-2-diethylaminomethylene-tetrahydropyran and 2-diethylamino-3-trifluoroacetyl-tetrahydropyran via an intramolecular nucleophilic addition reaction. Hydrazine and hydroxylamine attack the carbonyl carbon of the title compound to form (CH2)3OCH*CC(CF3)*NZ(Z=NH2, OH). In the presence of KOH, however, hydroxylamine hydrochloride reacts additionally to 2-hydroxyl-2-trifluoromethyl-3-cyano-tetrahydropyran. Upon heating with triethylphosphite, the title compound reacts as a heterodiene and gives the corresponding cyclophosphorane. X-Ray diffraction analyses of two compound are presented.
Zusammenfassung.
5-Trifluoracetyl-3,4-dihydro-2H-pyran reagiert bereitwillig mit vielen Nucleophilen wie Aminen oder Grignard-Verbindungen zu ringgeöffneten Produkten des Typs NuCH*CR 1 R 2 (R 1: (CH2)3OH, R 2: CF3CO). Die Verbindung mit R=Et2N ist instabil und lagert über eine intramolekuare nukleophile Additionsreaktion zum 1-Hydroxy-1-trifluormethyl-2-tetrahydropyran um. Hydrazin und Hydroxylamin greifen das Carbonylkohlenstoffatom der Titelverbindung an und geben dabei Verbindungen des Typs (CH2)3OCH*CC(CF3)*NZ (Z=NH2, OH). In Gegenwart von KOH reagiert Hydroxylamin jedoch zusätzlich zu 2-Hydroxy-2-trifluormethyl-3-cyano-tetrahydropyran. Bei Erhitzen mit Triethylphosphit reagiert die Titelverbindung als Heterodien zum entsprechenden Cyclophosphoran. Die beiden Verbindungen wurden mittels Röntgenstrukturanalyse charakterisiert.
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Received August 26, 1998. Accepted (revised) October 5, 1998
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Zhu, S., Xu, G., Qin, C. et al. On the Nucleophilic Reactions of 5-Trifluoroacetyl-3,4-dihydro-2H-pyran. Monatshefte fuer Chemie 130, 671–680 (1999). https://doi.org/10.1007/PL00010248
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DOI: https://doi.org/10.1007/PL00010248