Biginelli Product Research Articles

Demonstration of the feasibility of a direct solid-phase split-pool Biginelli synthesis of 3,4-dihydropyrimidinones.

[reaction: see text] A direct, Lewis acid-catalyzed Biginelli synthesis of 3,4-dihydropyrimidinones has been performed on high-capacity polystyrene macrobeads with a polymer O-silyl-attached N-(3-hydroxypropyl)urea. Resin-urea was first reacted separately with either 4-bromo- or 4-chlorobenzaldehyde and LiOTf in MeCN at 80 degrees C. After washing, the beads were pooled and reacted with ethyl acetoacetate and LiOTf in MeCN at 80 degrees C. Formation of only one kind of Biginelli product per bead demonstrated the feasibility of a solid-phase non-Atwal two-step split-and-pool synthesis of 3,4-dihydropyrimidinones.

New regioselective multicomponent reaction: one pot synthesis of spiro heterobicyclic aliphatic rings.

In the context of our high-throughput organic synthesis program, we have studied the reactivity of special beta-keto esters toward the Biginelli reaction. We have found that a cyclic beta-keto ester reacts with one molecule of urea and two molecules of aldehyde to give a new family of spiro heterobicyclic aliphatic rings in good yields. Interestingly, the Biginelli product was not detected. After analysis of products using HPLC, 1H NMR, and 13C NMR, we have found that the reaction is driven by a regio-specific condensation of two molecules of aldehyde with the other reagents to afford only products harboring substituents exclusively in cis configuration. Monte Carlo minimization studies using MM2 force field suggest that cis products are energetically more stable than the trans counterparts. Together with previously reported data, these results suggest that the trans products were not obtained as result of steric hindrance produced by the equatorial position of one of the ring substituents. This new reaction is useful for high-throughput organic synthesis. Indeed, the new scaffold can be used to introduce additional groups in the molecules through remaining functional groups by a "domino strategy".