79888-87-2Relevant academic research and scientific papers
Pyrylium Compounds. 32. 2-Methoxy-2H-thiopyrans from 2,4,6-Triaryl-thiopyrylium Salts
Zimmermann, Thomas,Fischer, Gerhard W.
, p. 373 - 379 (2007/10/02)
Reaction of 2,4,6-triarylthiopyrylium salts 1 with sodium methoxide in absolute methanol yields isolable 2-methoxy-2H-thiopyrans 2, the structure of which was proved spectroscopically.Using the 2,4,6-triphenyl derivative 2a as model compound, the behaviour of the 2-methoxy-2H-thiopyran system towards some nucleophiles and electrophiles was studied.Thus, on heating with ethanol the 2-ethoxy-2H-thiopyran 3 is formed.Nitromethane and ethyl cyanoacetate react with 2a in the presence of triethylamine to give 2,4,6-triphenylbenzene (6) and 2,4,6-triphenylbenzonitrile (7), respectively.Electrophiles (e.g. mineral acids or acyl halides) regenerate from 2a the starting thiopyrylium system; the same principle underlies the formation of 2,4,6-triphenyl-thiopyrylium perchlorate (1a) and 2-methoxy-3-methyl-2,4,6-triphenyl-2H-pyran (5) from 2a and 3-methyl-2,4,6-triphenylpyrylium perchlorate (4).
Pyrylium Compounds. XXIII. 2-Dialkylamino-2H-pyrans from Tetra- and Pentasubstituted Pyrylium Salts
Fischer, Gerhard W.,Zimmermann, Thomas,Weissenfels, Manfred
, p. 657 - 666 (2007/10/02)
Tetra- and pentasubstituted pyrylium salts of type 6 react with secondary alkyl amines to give stable crystalline 2-dialkylamino-2H-pyrans 7.In the case of tetrasubsituted pyrylium salts 6, R' = Me, R'' = H the reaction occurs regioselectively leading to 2H-pyrans with Me at C-3 of the heterocyclic ring.The structure of the reaction products was established by n.m.r., i.r., u.v. and mass spectroscopic methods.Electrophilic agents like protons, carboxylic acid chlorides or methyl iodide regenerate the original pyrylium cations from 7.In refluxing methanol 7a is converted into the 2-methoxy-2H-pyran derivative 8, whereas in aqueous acetone the pseudobase 9 and with ammonia the pyridine 10 are formed.Reaction of 7a with nitromethane or ethyl cyanoacetate provides the benzene derivatives 11 and 12, respectively.
