Sequential N-acylamide methylenation-enamide ring-closing metathesis: construction of benzo-fused nitrogen heterocycles.
The dimethyltitanocene methylenation of N-acylamides derived from ortho-vinylanilines, ortho-allylaniline, and ortho-vinylbenzylamine provides the corresponding enamides, which upon exposure to the second generation Grubbs ruthenium catalyst give access to indoles, 1,4-dihydroquinolines, and 1,2-dihydroisoquinolines, respectively. This sequential protocol also allows the synthesis of dihydrobenzoazepines, although the ring-closing metathesis (RCM) step is complicated by the alkene isomerization processes. From certain substrates, the direct annulation is observed in the titanium-mediated step, which is likely to occur through an olefin metathesis-intramolecular olefination sequence.
Bennasar
M Lluïsa
ML
Laboratory of Organic Chemistry, Faculty of Pharmacy, University of Barcelona, Barcelona 08028, Spain. bennasar@ub.edu
Roca
Tomàs
T
Monerris
Manuel
M
García-Díaz
Davinia
D
D000475:Alkenes / Q000737:chemistry; D001381:Azepines / Q000737:chemistry; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000138:chemical synthesis* / Q000737:chemistry; D002384:Catalysis; D002625:Chemistry, Organic / Q000379:methods*; D007211:Indoles / Q000737:chemistry; D009584:Nitrogen / Q000737:chemistry*; D011804:Quinolines / Q000737:chemistry; D012428:Ruthenium / Q000737:chemistry
D000475:Alkenes; D001381:Azepines; D019086:Bridged Bicyclo Compounds, Heterocyclic; D007211:Indoles; D011804:Quinolines; D012428:Ruthenium; D009584:Nitrogen