Synthesis of regioisomeric 2,5-bis-substituted-aza-benzothiopyranoindazoles

Citation
Ap. Krapcho et Sn. Haydar, Synthesis of regioisomeric 2,5-bis-substituted-aza-benzothiopyranoindazoles, J HETERO CH, 38(5), 2001, pp. 1153-1166
Citations number
20
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Organic Chemistry/Polymer Science
Journal title
JOURNAL OF HETEROCYCLIC CHEMISTRY
ISSN journal
0022-152X → ACNP
Volume
38
Issue
5
Year of publication
2001
Pages
1153 - 1166
Database
ISI
SICI code
0022-152X(200109/10)38:5<1153:SOR2>2.0.ZU;2-#
Abstract
The synthesis of 6-chloro-9-nitro-benzothiopyranopyridin-5-ones 2a, 2b and 2c has been accomplished. Chemotype 2d could not be prepared since attempts to cyclize 3-(2-nitro-5-chlorophenoxy)pyridine-2carboxylic acid (1d) led t o the decarboxylation product 3-(2-nitro-5-chlorothiophenoxy) pyridine (40) . Analogues 2a, 2b or 2c on treatment with the respectively substituted hyd razine led to the 2-(substituted)-5-nitro 7, 8- or 9-aza substituted chemot ypes 3a-7a, 8b, and 9c-13c. The reduction of the nitro groups of these subs trates was effected by treatment with hydrogen gas (palladium catalyst) or by stannous chloride to yield the 5-amino chemotypes 15a-18a, 20b and 21c-2 4c, respectively. The conversion of these derivatives to the 2,5-bis (alkyl amino)-7-, 8- and 9-aza benzothiopyranoindazoles listed in Table 3 was acco mplished by direct alkylations, acylations, followed by reduction of the am ido group with Red-Al or lithium aluminum hydride, or by reductive alkylati ons in the presence of sodium cyanoborohydride. The removal of the protecti ve BOC-group was effected by treatment of the appropriate substrates with a nhydrous hydrogen chloride to afford the respective hydrochloride salts lis ted in Table 4.