Other Asymmetric Isonitrile-based Multicomponent Reactions

Other Asymmetric Isonitrile-based Multicomponent Reactions 

Tandem Ugi or Passerini Reaction/lntramolecular Diels-Alder (IMDA) Cydizations 

Toward this goal, a furane ring was included in the carbonyl or amine component, since this moiety will furnish a highly reactive diene for the following IMDA. In most cases 2-furaldehyde (or the corresponding 5-methyl derivative) was employed. The acid component was chosen in order to introduce an activated dienophile suited for the IMDA and was in turn a fumaric acid monocarboxyamide [82, 84], a maleic or fumaric acid monoester [84] or a 3-substituted propynoic acid [83]. Benzylamine (or a para-substituted derivative) [81-83] or t-butylamine [83] have been chosen as amine component for the Ugi reactions. 

In addition, the bisallylation of the two secondary amides of compound 91, followed by treatment with an appropriate ruthenium catalyst, allowed a tandem ringopening metathesis/ring-closing metathesis to give, after alcohol deprotection, the quite complex structure 92 [82]. 

Interestingly, when the furane ring was present in the amine component, and 

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Other Asymmetric Isonitrile-based Multicomponent Reactions... 

If in Chapter 7 different aspects about Ugi reaction have been discussed, in this chapter, we are going to disclose to the reader a vision about the new contributions regarding other crucial isonitrile-based multicomponent reaction (MCR) the Passerini reaction (P-3CR) discovered in 1921 [1], The traditional multicomponent Passerini reaction [2] is another isonitrile-based MCR that provides easy access to a-acyloxycarboxamides 4 in a one-pot synthesis involving an aldehyde 1, a carboxylic acid 2, and an isonitrile 3 (Scheme 8.1), which has been subject of intensive studies in the last decade [3], The importance of using isocyanides lays in its dual role as nucleophile and electrophile, and moreover, if R R, a new stereocenter could be created under asymmetric conditions. 

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