[reaction: see text] The application of vinyloxiranes, substituted with an electron-withdrawing group, as masked dienolates in vinylogous imino-aldol reactions was achieved. Under the reaction conditions highly substituted 1,2-dihydropyridines were obtained in moderate to good yields. Mechanistic studies indicate that the reaction proceeds via the formation of an (E)-amino-alpha,beta-unsaturated aldehyde, followed by isomerization to the (Z)-isomer, cyclization, and elimination of a water molecule, leading to the formation of the 1,2-dihydropyridine.
A general route to linear triquinanes including a formal synthesis of (+/-)-Delta(9(12))-capnellene is described. This cascade strategy combines an intramolecular Diels-Alder reaction tandem metathesis protocol to generate the linear cis-anti-cis-tricyclo[6.3.0.0(2,6)]undecane skeleton directly. Significantly, the ring-closing-ring-opening-cross-metathesis (RCM-ROM-CM) sequence with our norbornene adducts is the only observed mechanism.
Pyridine derivatives R 0380Synthesis of 1,2-Dihydropyridines Using Vinyloxiranes as Masked Dienolates in Imino-Aldol Reactions. -A new one-pot procedure is developed for the synthesis of 1,2-dihydropyridines, selectively substituted at the 1, 2, 3, and 5 position. In some cases, low yields are observed due to hydrolysis of the aldimine substrates to aldehydes. The reaction at 0°C affords (E)-amino-α,β-unsaturated aldehydes. -(BRUNNER, B.; STOGAITIS, N.; LAUTENS*, M.; Org. Lett. 8 (2006) 16, 3473-3476; Davenport Res. Lab., Dep. Chem., Univ. Toronto, Toronto, Ont. M5S 3H6, Can.; Eng.) -R. Steudel 49-141
Metathesis (RCM) Dominates Norbornene ROM! -One-pot and stepwise methods are developed to prepare the target compounds (IV). The stepwise method and the first generation Grubbs' catalyst, are more efficient. -(NGUYEN, N. N. M.; LECLERE, M.; STOGAITIS, N.; FALLIS*, A. G.; Org. Lett. 12 (2010) 8, 1684-1687, DOI:10.1021/ol100150f ; Dep. Chem., Univ. Ottawa, Ottawa, Ont. K1N 6N5, Can.; Eng.) -R. Steudel 35-065
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