Wang resin-supported dipolarophile

Wang resin supported nitrile oxides, generated from resins 42, displayed increased stability and could be isolated or directly trapped with a variety of dipolarophiles. The cleaved adducts, such as 44, were recovered by treatment of the resin 43 with TFA O2EJ01175>. 

Additional examples of libraries of isoxazolines prepared by 1,3-dipolar cycloaddition of Wang resin-<1998TL939> or chlorotrityl resin- <1998TL2447> supported dipolarophiles, generated in the presence of a variety of dipolarophiles, have been reported. The achiral hydantoin- and isoxazoline-substituted bis-spirocyclobutanoids 458 and 459 were produced using SPS (Scheme 105) <2000CC1835>. 

In view of the multicomponent nature of the tandem [4 + 2] / [3 + 2] cycloaddition, the potential for a combinatorial approach to the synthesis of nitroso acetals has been investigated on solid-phase supports. The incorporation of either the dipolarophile or the starting nitroalkene on a Wang-type resin is compatible with the tandem cycloaddition promoted at high pressures (Schemes 2.28 and 2.29). The solid-supported nitroso acetals are subsequently liberated (in moderate yields from the staring nitroalkene) upon the addition of a catalytic amount of potassium cyanide in triethylamine and methanol or by reduction with lithium aluminum hydride (LAH) (261,264). 

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