2- furan, reaction with ethyl acrylate

Vinylbenzo[7]furans, 3-vinylfuropyridines, and 3-vinylindoles were employed as conjugated dienes in the Diels-Alder reaction with ethyl acrylate, affording tricyclic adducts in fair to good yields, as shown in Equation (103) <20020L2791>. 

Approaches to oseltamivir phosphate (1) that were independent of ( )-shikimic acid as the raw material were also evaluated. The furan-ethyl acrylate Diels-Alder approach is shown in Scheme 7.8 (Abrecht et al., 2001, 2004). The zinc-catalyzed Diels-Alder reaction between furan and ethyl acrylate was heated at 50°C for 72 h to provide a 9 1 mixture favoring exo-isomer rac-43 over the enJo-isomer. The enJo-isomer was kinetically preferred, but with increased reaction times an equilibrium ratio of 9 1 was achieved favoring the thermodynamically preferred exo-isomer rac-43. The optical resolution of rac-43 was achieved via enantioselective ester hydrolysis using Chirazyme L-2 to give (—)-43 in 97%... 

Attempts to isolate 2,3-dimethoxyfuran (156) have, as yet, been fruitless (79JCS(P1)1893), but it may be generated in situ and trapped with the propiolate (155) the initial adducts (157) are unstable under the acidic conditions and yield the biphenyls (158) and (159) (Scheme 67). 2,5-Bis(trimethylsilyloxy)furans, readily available from succinic anhydrides in one step, are also more reactive than furan in Diels-Alder reactions (80TL3423). They readily undergo reaction with both DMAD and ethyl acrylate. Thus at 50 °C in carbon tetrachloride the furan (160) with DMAD followed by detrimethylsilylation gave only the quinone (163). At 80 °C, however, the hydroquinone (164) is the major product. Both the intermediates (161) and (162) may be detected by ]H NMR spectroscopy. The formation... 

TMSOTf promotes the Diels-Alder cycloaddition of /7-tolyl vinyl sulfoxide with furan or cyclopentadiene the reaction is slower and less stereoselective than when induced by ethyl Meerwein s reagent (EtsOBFa). It also promotes the [4 + 2] cycloaddition between 2,2-dimethoxyethyl acrylate and several... 

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