Enantio- and diastereoselective synthesis of 2,5-disubstituted pyrrolidines through a multicomponent Ugi reaction and their transformation into bicyclic scaffolds

“…The addition of imines (instead of forming them in situ) allows the participation of a variety of heterocyclic structures, which could not otherwise be prepared in a straightforward manner. [44] In this regard, the use of dihydropyridines and cyclic enol ethers is also promising, as they can be activated by electrophiles to generate the cationic species ready to interact with the isocyanides and give the adduct. [45] The mixing of iodine, isocyanides and 1,4-dihydropyridines produced an unexpected result: a complex cascade process led to rearranged benzimidazolium systems in high yields (Scheme 23).…”

Section: Isocyanide-based Reactionsmentioning

confidence: 99%

Heterocycles as Key Substrates in Multicomponent Reactions: The Fast Lane towards Molecular Complexity

Isambert

Lavilla

2008

Chemistry A European J

309

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Heterocycles display an intrinsic reactivity which enables rich, versatile and productive transformations. Taking into account their ubiquitous presence in natural products and drugs, the development of new, fast and efficient preparative protocols for these structures remains an urgent task in Organic Synthesis. Multicomponent reactions using heterocyclic chemistry offer new possibilities to exploit this exclusive reactivity. Recent results show relevant examples of such transformations. Several approaches which allow the construction of complex heterocyclic compounds from simple starting materials using this principle have been analyzed.

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“…Peptides can be efficiently synthesized, in a stereoselective manner, through the Ugi five-center-four-component reaction (U-5C-4CR), using isocyanides, aldehydes, and α-amino acids as bifunctional starting materials. 68 Heterocyclic oligopeptide analogs can be prepared by the Ugi reaction of t-butyl isocyanide, carboxylic acids, and 2,5-dihydro-1,3-thiazoles, 2,5-dihydro-1,3-oxazoles, or 2H-1,3-oxazines, as the imine components. The stereoselective synthesis of peptide derivatives is also achieved through the classical Ugi four-component condensation (U-4CC) using chiral sugar auxiliaries, together with ZnCl 2 catalysis.…”

Section: %mentioning

confidence: 99%