CHEMOSELECTION CONTROL OF DIELSALDER REACTIONS USING TWO CONJUGATE DIENES

建立了用两种共轭双烯控制Diels-Alder反应化学选择性的合成方法，根据反应条件的不同，这两种双烯都可以作为双烯和亲双烯。化学选择性和其他选择性，如区域选择性和非对映选择性，有两种可能的组合。我们研究了两种不同的共轭二烯，如无环和环二烯在不同催化剂存在下的反应。选择了2-甲基-1，3-丁二烯、2，3-二甲基-1，3-丁二烯和环戊二烯作为共轭1，3-二烯；使用了与1，3-偶极相同的亲核试剂如1，3-二烯和硝基。在使用这些共轭双烯和硝酮偶极环加成这些共轭双烯的Diels-Alder反应中，各种Lewis酸催化剂，如卤素本身、含非配位卤离子的卤离子、N-卤代铵和N-卤代吡啶盐已被大量应用。然而，这些催化剂都不能有效地活化反应。相应的卤化物衍生物与四氟化硼银反应生成的硅基阳离子、硫阳离子和硒离子都不能加速反应。烯丙基乙酸酯和碳酸盐在零钯催化剂存在下生成烯丙基阳离子物种，并允许与共轭双烯和硝酮反应。然而，还没有观察到具体的效果。

Establishment of a synthetic method for chemoselectivity control in Diels-Alder reactions using two kinds of conjugate dienes, both of which can act as dienes and dienophiles depending upon the reaction conditions. Two possible combinations are possible for the chemoselectivity, and other selectivities such as regio- and diastereoselectivities. We have investigated the reactions using two different conjugate dienes, such as acyclic and cyclic ones, in the presence of a variety of catalysts.2-Methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, and cyclopentadiene have been selected as conjugate 1,3-dienes; nucleophiles such as the same 1,3-dienes and nitrones as 1,3-dipole have been used.. For the Diels-Alder reactions using these conjugate dienes and nitrone dipolar cycloadditions toward these conjugate dienes, a variety of Lewis acid catalysts such as halogens themselves, halonium ions having noncordinating halonium ions, N-haloammonium and N-halopyridinium salts have been applied in catalytic amounts. However, these catalysts are all ineffective for the activation.Silyl cations, sulfonium cations, and selenium cations, which have been generated in situ by interaction of the corresponding halide derivatives with silver borontetrafluoride, have failed to accelerated the reactions. Allylic cation species have been generated from allylic acetates and carbonates in the presence of palladium zero catalysts and allowed to react with conjugate dienes and nitrones. However, no specific effect has not been observed.