jo050964e_si_001.cif (13.94 kB)
Synthesis of 2H-1,2-Benzothiazine 1,1-Dioxides via Heteroannulation Reactions of 2-Iodobenzenesulfonamide with Ketone Enolates under SRN1 Conditions§
dataset
posted on 2005-11-11, 00:00 authored by William J. Layman,, Thomas D. Greenwood, Aaron L. Downey, James F. Wolfe2-Iodobenzenesulfonamide (1a) underwent photostimulated SRN1 reactions in liquid NH3 with the
potassium enolates derived from acetone, pinacolone, butanone, and 3-methyl-2-butanone to give
fair to good yields of 2H-1,2-benzothiazine 1,1-dioxides 2. Reductive dehalogenation of 1a was found
to predominate in photoinduced reactions of 1a with 3-pentanone, 2-methyl-3-pentanone, and 2,4-dimethyl-3-pentanone, the extent of reduction being proportional to the number of β-hydrogen atoms
present in the ketone enolate. Isotopic labeling studies with 2,4-dimethyl-3-pentanone-d14 (24)
confirmed the major role of the β-hydrogens in the reduction process. Reactions of 1a with
cyclopentanone, cyclohexanone, and cyclooctanone enolates afforded new tricyclic benzothiazine
derivatives 26−29. Attempts to extend the heteroannulation reaction to the preparation of 2H-1,2-benzothiazin-3(4H)-one 1,1-dioxides 3 (R = H, Ph) through reactions of 1a with tert-butyl acetate
and ethyl phenylacetate enolates resulted only in hydrodehalogenation of 1a. However, oxazoline
anion 30, a synthetic equivalent of ethyl phenylacetate, was successfully employed in an alternative
SRN1-based synthesis of benzothiazine 3 (R = Ph).
History
Usage metrics
Categories
Keywords
heteroannulation reactionbutyl acetatemethylKetone Enolatesketone enolateethyl phenylacetatePhHeteroannulation Reactionsdioxidephotostimulated S RN 1 reactionsReductive dehalogenationbenzothiazine 3NH 3dimethylethyl phenylacetate enolatesreduction processIodobenzenesulfonamidephotoinduced reactionspotassium enolatesoxazoline anion 30cyclooctanone enolates
Licence
Exports
RefWorks
BibTeX
Ref. manager
Endnote
DataCite
NLM
DC