Hydro-, halo- and seleno-carbamoylation of cyclic enol ethers and dihydropyridines: New mechanistic pathways for Passerini-and Ugi-type multicomponent reactions
I. Ugi, S. Lohberger, R. Karl, in: B. M. Trost, I. Fleming (Eds.), Pergamon Press, Oxford, chapter 4
a) I. Ugi, S. Lohberger, R. Karl, in: B. M. Trost, I. Fleming (Eds.), Comprehensive Organic Synthesis, Pergamon Press, Oxford, 1991, Vol. 2, chapter 4;
The presence of an electron-withdrawing group at the β-position is needed for the stability of the compounds. For a recent review on the chemistry of dihydropyridines, see: R. Lavilla, J. Chem. Soc., Perkin Trans, 1 2002, 1141.
Preformed imines and enamines have been used in Ugi reactions. For instance, see: a) M. M. Bowers, P. Carroll, M. M. Jouillé, J. Chem. Soc., Perkin Trans. 1 1989, 857;
When we used (+)-camphorsulfonic acid as the catalyst, we observed a very low enantiomeric excess (2%), as determined by chiral HPLC.
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The interaction of acetals with isocyanides under acid catalysis has been reported. See: H. Pellissier, A. Meou, G. Gil, Tetrahedron Lett. 1986, 27, 2979.
This compound showed a single relative stereochemistry which was not determined. Presumably displaying the iodo and the carbamoyl substituents on opposite faces.
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For the related interaction of arylsulfenyl chlorides with isocyanides, see: G. Morel, E. Marchand, K. H. Nguyen Thi, A. Foucaud, Tetrahedron 1984, 40, 1075.
J. Zhu, H. Bienaymé (Eds.), Wiley-VCH, Weinheim, chapter 2
For an excellent review on the subject, see: S. Marcaccini, T. Torroba, in: J. Zhu, H. Bienaymé (Eds.), Multicomponent Reactions, Wiley-VCH, Weinheim, 2005, chapter 2.
These DHP display electron-withdrawing groups at the α-and β′-positions. Recently the synthesis of α-substituted DHPs was reported: E. Gómez, M. Miguel, O. Jiménez, G. de la Rosa, R. Lavilla, Tetrahedron Lett. 2005, 46, 3513.