88320-34-7Relevant articles and documents
The "tert-amino effect" in heterocyclic chemistry: synthesis of 3,1-benzoxazines and 3,1-benzothiazines
Nijhuis, W. H. N.,Verboom, W.,Harkema, S.,Reinhoudt, D. N.
, p. 147 - 160 (2007/10/02)
Two different routes are described for the synthesis of the 2,2,2-trifluoro-1-ethanones 2 and 9 and their hydrates 3 and 10, respectively, via trifluoroacetylation of the N,N-dialkylanilines 1 and via a Barbier reaction of 2-fluorobenzaldehyde.These compounds were thermally converted into a mixture of cis- and trans-pyrrolo- and pyridobenzoxazines, (11: cis, 12: trans).The structure of these compounds was proven by X-ray analysis (11a) and 1H NOE difference spectroscopy.Cyclization of (R)-9b (R1 = CH3) gave predominantly one enantiomer (12f, 70percent) and in addition two diastereomers of 17a and two of 18a (total yield ca. 17percent), while cyclization of (S)-9c (R1 = CH2OCH3) gave a mixture of 12g (18percent), two diastereomers of 17b (36percent) and two diastereomers of 18b (18percent).The benzaldehyde 19a (R3 = H), acetophenone 19d (R3 = CH3), trifluoroacetophenones 19b,c (R3 = CF3) and benzophenone 19e (R3 = C6H5) reacted with Lawesson's reagent to yield exclusively the trans-pyrrolobenzothiazines 21a-e in yields of 33-77percent.Reaction of 19f (R1 = CH3, R3 = H), 19g (R1 = CH3, R3 = CF3) and 19h (R1 = CH3, R3 = CH3) with Lawesson's reagent resulted in the formation of mixtures of isomers 21-24.
