40814-66-2Relevant articles and documents
An Intramolecular Wittig Approach toward Heteroarenes: Synthesis of Pyrazoles, Isoxazoles, and Chromenone-oximes
Khairnar, Pankaj V.,Lung, Tsai-Hui,Lin, Yi-Jung,Wu, Chi-Yi,Koppolu, Srinivasa Rao,Edukondalu, Athukuri,Karanam, Praneeth,Lin, Wenwei
supporting information, p. 4219 - 4223 (2019/06/17)
α-Halohydrazones/ketoximes are transformed into trisubstituted pyrazoles/disubstituted isoxazoles by treatment with phosphine, acyl chloride, and a base. Mechanistic investigations revealed the in situ formation of azo/nitroso olefin intermediates which underwent a tandem phospha-Michael/N- or O-acylation/intramolecular Wittig reaction to afford the heteroarenes in moderate to good yields. Further, proper functionalization of α-haloketoximes and a change of conditions allowed the chemoselective synthesis of chromenone-oximes as well as rearranged isoxazoles, thereby realizing a diversity-oriented synthesis.
Synthesis of 6-ethoxy-6H-1,2-oxazines by hetero Diels-Alder reaction of 1-bromo-2-ethoxyethene with α-nitroso alkenes
Homann, Kai,Angermann, Joerg,Collas, Markus,Zimmer, Reinhold,Reissig, Hans-Ulrich
experimental part, p. 649 - 655 (2011/10/09)
A variety of 6H-1,2-oxazines 10 could efficiently be prepared by hetero Diels-Alder reaction of α-nitroso alkenes 2 with 1-bromo-2-ethoxyethene (8) and consecutive elimination of HBr by DBU. Heterodienes 2 were generated in situ from α-halogen oximes 6. Primary cycloadducts 9 were isolated in singular cases, however, an attempt to substitute bromide in 9e by an azido group gave the desired compound 11 only as minor component together with elimation product 10e. 6H-1,2-oxazines 10 are valuable precursors for addition reactions which open new synthetic possibilities.