Development of New Organic Reactions by Use of Electron Acceptor Quinones

[2+2]光环化加成反应：用乙基乙烯基醚辐照各种间位和对位取代的均苯醌，区域选择性和内位选择性地得到[2+2]光环化加成物。加合物具有通过从高苯醌的较少受阻侧添加乙基乙烯基醚而构建的反式。反应中C = C双键上的CH_3、Cl、Br和CH_3O取代基主要发生头对头加成反应。在CH_3，Cl和Br的情况下，乙氧基在内位上是-取向的，而CH_3O取代基则与外位异构体形成1/5的混合物。同时发现，Br取代的[2+2]加成物在原位生成的HBr的影响下，发生了简单的骨架重排，生成对位取代的二氢苯醌甲基化物和间位取代的二氢邻苯并呋喃衍生物，并研究了15-21元喹啉冠醚1a-c和18元喹啉苯并冠醚1d与环己基的Diels-Alder反应 ...更多信息 通过加入碱金属、碱土金属和高氯酸铵以及三氟甲磺酸钪来催化戊二烯。碱金属离子对每种冠醚都具有相当高的选择性加速作用，这是由于它们之间存在着尺寸匹配的空穴离子络合作用。然而，在二价碱土金属（Mg^2+到Ba^2+）和三价Sc^3+催化的反应中，没有观察到这种空穴尺寸选择性。包裹络合作用在速率加速中起着重要作用，最小的Mg^<2+>对最灵活的1c的速率提高了160倍，Sc^<3+>对18元喹啉并冠1d的速率提高了3700倍。这些阳离子识别的效果是合理的减少LUMO能量，这是有利于轨道相互作用与环戊二烯的HOMO。速率增强的幅度解释的阳离子结合亲和力和醌冠醚的配位几何形状以及阳离子的价态。少

[2+2] photocycloaddition: Irradiation of various meto- and para-substituted homobenzoquinones with ethyl vinyl ethers gave the [2+2] photoadducts regio- and endo-selectively. The adducts have an antiform built by the addition of ethyl vinyl ethers from the less hindered side of homobenzoquinones. All of the CH_3, Cl, Br, and CH_3O substituents at the reacting C = C double bond afforded head-to-head addition predominantly. In the case of CH_3, Cl, and Br, the ethoxy group was -oriented in the endoposition, while the CH_3O substituent led to a 1/5 mixture with the exo-isomer. It was also found that the Br-substituted [2+2] adducts undergo a facile skeletal rearrangement, being converted into dihydro-obenzoquinone methide for para-substituent and dihydro-o-benzofuran derivatives for meta-substitution, probably under the influence of the in sit generated HBr.Diels-Alder reactions of quinocrown ethers: 15-21-membered auinocrown ethers 1a-c and 18-membered quinobenzocrown ether 1d with cyclo … More pentadiene were catalyzed by the addition of alkali, alkaline earth metal and ammonium perchlorates, and scandium trifluoromethane-sulfonate. The alkali metal ions brought about a fairly selective rate-acceleration for each crown ether due to the size-fitted ion-in-the-hole complexation. However, such a hole-size-selectivity was not observed for the reactions catalyzed by divalent alkalie earth (Mg^<2+> to Ba^<2+>) and trivalent Sc^<3+> ions. The wrapping complexation played a significant role in rate-acceleration in such a way that the smallest Mg^<2+> caused 160 times rate-enhancement for the most flexible 1c and the Sc^<3+> performed maximal 3700 times rate-increment for the 18-membered quinobenzocrown 1d. These effects of cation recognition were rationalized by the reduction of LUMO energy that is favored by the orbital interaction with the HOMO of cyclopentadiene. The magnitude of rate-enhancement was expained in terms of the cation binding affinity and coordination geometry of quinocrown ethers as well as the valence of cations. Less