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. 2018 Aug 24:6:376.
doi: 10.3389/fchem.2018.00376. eCollection 2018.

A Five-Component Biginelli-Diels-Alder Cascade Reaction

Affiliations

A Five-Component Biginelli-Diels-Alder Cascade Reaction

Taber S Maskrey et al. Front Chem. .

Abstract

A new multi-component condensation was discovered during the reaction of a urea, β-keto ester, and formaldehyde. In the presence of catalytic indium bromide, a Biginelli dihydropyrimidinone intermediate was further converted to a five-component condensation product through a formal hetero Diels-Alder reaction. The product structure was confirmed by NMR and NOE analysis, and the proposed stepwise mechanism was supported by the reaction of the Biginelli intermediate with ethyl 2-methylene-3-oxobutanoate.

Keywords: 5-CC; Biginelli reaction; InBr3; dihydropyrimidinone; hetero Diels-Alder reaction; multi-component condensation.

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Figures

Figure 1
Figure 1
DHPM structure and biologically active analogs.
Figure 2
Figure 2
Literature precedence and synthetic plans.
Figure 3
Figure 3
Five-component condensation reaction. For conditions, see Table 1.
Figure 4
Figure 4
Attempted five-component condensation reaction with a cyclic 1,3-diketone.
Figure 5
Figure 5
Stepwise conversions of intermediate DHPM (Biginelli) products in a hetero Diels-Alder reaction.
Figure 6
Figure 6
Retro Diels-Alder reaction under Krapcho dealkylation conditions.
Figure 7
Figure 7
Proposed mechanism of five-component condensation.

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