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Synthesis of dihydrothieno[2,3‐ b ]pyridines based on titanium(IV) chloride‐mediated michael reactions of 2‐amino‐4,5‐dihydro‐3‐thiophenecarbonitriles with α,β‐unsaturated ketones
Author(s) -
Maruoka Hiroshi,
Yamazaki Motoyoshi,
Tomioka Yukihiko
Publication year - 2004
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.5570410428
Subject(s) - chemistry , titanium , yield (engineering) , aromatization , medicinal chemistry , ketone , alcohol , adduct , intramolecular force , potassium , methyl vinyl ketone , chloride , michael reaction , organic chemistry , acetyl chloride , catalysis , materials science , metallurgy
2‐Arnino‐4,5‐dihydro‐3‐thiophenecarbonitriles 1a‐c reacted with α,β‐unsaturated ketones ( e.g. methyl vinyl ketone 2 and benzalacetone 3 ) in the presence of titanium(IV) chloride to give the corresponding Michael adducts 4a‐c and 5a‐c. Thermal treatment of compounds 4a‐c and 5a‐c with titanium(IV) chloride caused intramolecular cyclocondensation to yield the corresponding tetrahydrothieno[2,3‐ b ]pyridines 6a‐c and 7a‐c. Aromatization of 6a‐c and 7a‐c with potassium tert ‐butoxide in refluxing tert ‐butyl alcohol pro ceeded smoothly to afford the corresponding dihydrothieno[2,3‐ b ]pyridines 8a‐c and 9a‐c.