Based on the reactive bahavour of the substrates, two synthetic routesto polysubstituted pyrimidine derivatives are presented herein: 1) A catalyst-ree multicomponent reaction of electron-deficient alkynes, aliphatic amines and formaldehyde and 2) Ag1- catalyzed synthesis of pyrimidines from electron-deficient alkynes, anilines and formaldehyde by a domino reaction. Under optimized conditions, the multicomponent reactions were accomplished with high regioselectivity and excellent yields. A computational study was carried out by using the B3LYP demsity functional theory to elucidate the mechanisms of the catalyst-free hydroamination reaction. Calculations showed the activation free energies of aliphatic amines were lower than those of anilines, which is consistent with the experimental results.

The Wacker reaction is a good way to produce methyl ketones via the PdII-catalyzed oxidation of terminal olefins.1 In order to improve the activity of the catalyst in the Wacker reaction, many efforts have been made,1 including (1) choice of solvents, such as N,N-dimethylformamide (DMF),2 ethanol,3 acetonitrile (CH3CN),4 and supercritical carbon dioxide (scCO2),5 (2) addition of hexamethylphosphoramide (HMPA),6 (3) substitution for cocatalyst CuCl2 (or CuCl) using benzoquinone (BQ),4 ferric chloide,7 heteropoly acid (HPA),8 ironphthalocyanine (FePc),9 and (4) the supporting of PdII catalyst by polymers.10 Of all the improvements to the PdII-catalyzed Wacker reaction, more and more importance has been attached to the utilization of BQ11 instead of cocatalyst CuCl2 (or CuCl) owing to two other advantages: (1) reducing the quantity of chlorine ion in the reaction solution, which is beneficial to avoid the erosion of metallic reactors and by-products caused by chlorination, and (2) preventing the interference of copper ion in the recovery of precious metal palladium from the remains. Therefore, the substitution of BQ for CuCl2 in the Wacker reaction or similar oxidation of alkenes has been successfully reported by Ba¨ckvall et al.4,12 However, as a small organic molecule, BQ can influence the separation of reaction products and recovery of palladium. If BQ could been fixed on polymer, the process would be simpler. Unfortunately, there have been only a few papers reported on BQ fixed on polymers and its application in the Wacker reaction in a long time.13 Many acetals, such as alkyl 3,3-dialkoxypropanoates, b-ketoacetals and b-cyanoacetal, are important intermediates in organic synthesis and have been used to synthesize a variety of compounds, including coumarins, porphyrins, spermine metabolites, loganin,14 and active cyclic enaminone derivatives, drugs for prevention and treatment of ischemic heart diseases, dyes, pharmaceuticals and auxiliary agents in textile indusrties.15 Of all the methods to prepare these compounds with 3,3-dialkoxy group, the PdII-catalyzed reaction between terminal olefins with electron-withdrawing groups and alcohols as a new type of Wacker reaction is the simplest one.16 In the initial stage, high yield of acetals, such as methyl 3,3-dialkoxypropanoate (92%), must be afforded in DMF and in the presence of expensive and toxic HMPA. Once HMPA was absent, the yield was only 46%.14 As a green reaction solvent, scCO2 has many well-known advantages.5,17 Recently, replacing DMF with scCO2 was realized in the synthesis of methyl 3,3-dimethoxypropanoate according to Hosokawa et al.’s work.16 The result was successful as expected, and the conversion and selectivity was excellent, especially without the non-green reagent HMPA.18 Based on our previous work in scCO2,5,18,19 in this paper we wish to report the studies on application of polymer-supported benzoquinone (PS-BQ) to PdII-catalyzed acetalization of terminal olefins with electron-withdrawing groups in scCO2.