Biomedical Engineering Reference
In-Depth Information
SCHEME 2.5
MCR reported by Stoltz's group [27] involving arynes and isocyanides leading
to the formation of phenoxyiminoisobenzofurans or iminoindenones.
Although many of the recently disclosed MCRs have been inspired by the Ugi
and Passerini reactions, the isonitrile components of these MCRs are often difficult
to work with, due to their highly unpleasant odor. Several novel isonitrile-free MCRs
have been developed in recent years that use other highly reactive components, such
as amines and highly enolizable carbonyl compounds. A recent report by Wei and
Shaw of a 4CR between aldehydes, amines, thiols, and maleic anhydrides to produce
-lactams is one example [31]. Both tetra- and penta-substituted lactams were
obtained in high yield and diastereoselectivity, with water as the only by-product
(Scheme 2.7).
In another recent example, benzaldehydes, malononitrile (or ethyl cyanoacetate),
6-methyl-2,3,4,9-tetrahydro-1
H
-carbazol-1-one, and ammonium acetate react in the
presence of L-proline to form pyridocarbazoles [32]. The carbazole heterocycle is a
scaffold found in many biologically active compounds of diverse origins, and chemists
have been interested in these structures because of their potential applications as
pharmaceutical agents [33]. Although the benzaldehyde is the only component that
SCHEME 2.6
MCR reported by Sha and Huang [29] involving arynes and isocyanides,
leading to the formation of polysubstituted pyridines and isoquinolines.
