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  • 1,2-Oxazines  (1)
  • Oximes
  • Wiley-Blackwell  (1)
  • 1990-1994  (1)
  • 1994  (1)
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  • Wiley-Blackwell  (1)
Years
  • 1990-1994  (1)
Year
  • 1
    ISSN: 0009-2940
    Keywords: 1,2-Oxazines ; Bromination, radical ; SN2 reaction ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 5,6-Dihydro-4H-1,2-oxazines 1a-b, 2, and 3 are easily brominated at C-4 with N-bromosuccinimide/dibenzoyl peroxide in tetrachloromethane. The bromo substituent is incorporated with surprisingly high diastereoselectivity trans to the substituent at C-6. 4-Bromo-5,6-dihydro-4H-1,2-oxazines are useful reagents for substitution reactions with N-nucleophiles such as primary amines and azide ions. Inversion of configuration at C-4 provides derivatives of 4-amino-1,2-oxazines with uniform relative configuration. As a minor byproduct the dibromo adduct 7 is obtained by bromination of 3. The dehydrohalogenation of this compound allows the synthesis of the 4-bromo-6H-1,2-oxazine 12. The presented reaction sequence thus constitutes an “umpolung” reaction that allows the introduction of nucleophiles into a position of the oxazine ring that so far was accessible only for electrophiles. The diastereoselectivity of the bromination reaction is discussed.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
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