Reactions of 1,1-dihaloalkenes with triorganozincates: a novel method for the preparation of alkenylzinc species associated with carbon-carbon bond formation
摘要:
Lithium trialkylzincates react with 1,1-dibromoalkenes 1 and 1-bromo-1-chloroalkenes 2 at -85-degrees-C in THF to give 1-bromoalkenes 5 and 1-chloroalkenes 7, respectively, upon hydrolysis. The intermediate (1-haloalkenyl)zincates 4 and 6 are stable at low temperature but, when allowed to warm to 0-degrees-C, they undergo a 1,2-alkyl migration reaction to afford alkenylzinc species 10. A variety of alkylation products 11 are obtained by the hydrolysis of 10. In the presence of (Ph3P)2Pd (5 mol%), alkenylzinc species 10 react smoothly with organic halides (AcCl, EtOCOCl, CH2=CH-(Me)Br, PhBr) to yield the corresponding coupling products 13-16.
A new Suzuki synthesis of triphenylethylenes that inhibit aromatase and bind to estrogen receptors α and β
作者:Li-Ming Zhao、Hai-Shan Jin、Jinzhong Liu、Todd C. Skaar、Joseph Ipe、Wei Lv、David A. Flockhart、Mark Cushman
DOI:10.1016/j.bmc.2016.08.064
日期:2016.11
The design and synthesis of dual aromataseinhibitors/selective estrogen receptor modulators (AI/SERMs) is an attractive strategy for the discovery of new breast cancer therapeutic agents. Previous efforts led to the preparation of norendoxifen (4) derivatives with dual aromatase inhibitory activity and estrogen receptor binding activity. In the present study, some of the structural features of the
Palladium-catalyzed cross-couplingreaction of 1,1-diboryl-1-alkenes with aryl and alkenyl iodides was found to proceed stereoselectively, giving rise to the corresponding mono-coupled product as a single diastereomer with E-configuration. Second coupling of the initial product with another aryl iodide affords diverse triarylalkenes in their stereochemically pure form. This highly stereoselective approach
发现钯催化的 1,1-二硼基-1-烯烃与芳基和烯基碘化物的交叉偶联反应立体选择性地进行,产生相应的单偶联产物,作为具有 E 构型的单个非对映异构体。初始产物与另一种芳基碘化物的第二次偶联得到立体化学纯形式的各种三芳基烯烃。这种三芳基烯烃的高度立体选择性方法允许人们在一个锅中从 1,1-二硼基-1-烯烃合成两种非对映异构体。
Stereochemistry in carbenoid formation by bromine/lithium and bromine/zinc exchange reactions of gem-dibromo compounds
bromine/lithium and bromine/zinc exchangereactions take place preferentially at the sterically more hindered bromine atom of the starting gem-dibromo compounds. The observation is rationalized by an exchange mechanism involving a linear transition state of either an ate complex formation or an SN2 reaction at the more hindered bromine atom where strain relief due to the elongation of the carbon-bromine bond is
通过宝石的溴/金属交换反应生成锂和锌酸类胡萝卜素的立体化学已经研究了分别与BuLi和三有机锌酸锂形成的二溴化合物。已证明,衍生自1,1-二溴烯烃的锂和锌酸酯类化合物在低温下是构型稳定的,而在未反应的起始二溴烯烃的存在下,锂类化合物而不是锌酸酯类化合物在类胡萝卜素碳上容易进行异构化。在起始二溴环丙烷存在下,衍生自1,1-二溴环丙烷的Zincate类胡萝卜素在类胡萝卜素碳上缓慢进行异构化。事实证明,锂和锌酸盐类胡萝卜素的异构化反应是通过涉及类胡萝卜素与起始二溴化合物之间的溴/金属交换的机理进行的。在1,1-二溴烯烃在热力学条件下的反应中观察到锂类胡萝卜素的高度立体选择性形成。在动力学控制的条件下,溴/锂和溴/锌的交换反应均优先发生在起始位点的空间受阻溴原子上宝石-二溴化合物。通过交换机制合理化该观察,该交换机制涉及在受阻溴原子处的盐配合物形成或S N 2反应的线性过渡态,在这种情况下,由于碳-溴键的延长,应力会减轻。
Olefination of aromatic ketones: synthesis of mono- and dihaloalkenes
作者:Vasily N. Korotchenko、Alexey V. Shastin、Valentine G. Nenajdenko、Elisabeth S. Balenkova
DOI:10.1039/b201131j
日期:2002.3.25
A new simple and efficient transformation of various aromatic ketones to the corresponding halo (dihalo) alkenes is described. The reaction proceeds under mild conditions to give the target products in good yields.
Palladium-catalyzeddoublecross-couplingreactions of 1,1-bis(pinacolato)borylalk-1-enes with 2,2′-dibromobiaryls and of 9-stannafluorenes with 1,1-dibromoalk-1-enes have been demonstrated to serve as new synthetic methods for dibenzofulvenes.