Functionalization of Meldrum’s Acid by Diels‒Alder Approach

Abstract

We have synthesized several Meldrum's acid derivatives using Diels-Alder reaction as a key step. Here, the key sultine derivative is prepared by rongalite and the sultine derivative is useful as a latent diene.Meldrum's acid, 2,2-dimethyl-1,3-dioxane-4,6-dione, a cyclic ester, with an acidic CH2 group with pKa 4.83 1,2 is valuable synthon to design heterocycles and polycycles. 3 It is widely used in multicomponent reactions. 4 Meldrum's acid derivatives are also beneficial to assemble natural products and also used for synthesis of reactive intermediates and polymers. 5 They are also used in aza-Diels-Alder reaction with different dienophiles. 6 Uracil derivatives 7 are synthesized from trifloroacetyl Meldrum's acid. Gillena and co-workers 8 recently synthesized an antimicrobial compounds from Meldrum's acid. Various Meldrum's acid derivatives 1-5, shown in Figure 1 are useful in designing diverse polycycles. 9-18 Figure 1. Meldrum's acid derivatives used in organic synthesisRecently, Kotha and co-workers reported diverse Meldrum's acid derivatives involving a [2+2+2] cycloaddition reaction as a key step. Compound 4 undergo ring-closing metathesis (RCM) to generate cyclopentene derivative 6. Whereas, dialkyne derivative 5 and monoalkyne 7 undergo cyclotrimerization to generate the dibromo compound 8 with the aid of Mo(CO)6 (Scheme 1) under microwave irradiation conditions in acetonitrile. 19,20 Furthermore, we developed a new route for the synthesis of tetrahydroisoquinoline carboxylic acid derivatives via a [2+2+2] cyclotrimerization. 21,22 In view of our

Selectivity: A Goal for Synthetic Economy

“…A similar strategy was applied to indole derivatives to deliver symmetrical compound 155 as well as unsymmetrical compound 156 (Scheme 33). 44 Scheme 33…”