Syntheses of Seven-Membered Rings: Ruthenium-Catalyzed Intramolecular [5+2] Cycloadditions
作者:Barry M. Trost、Hong C. Shen、Daniel B. Horne、F. Dean Toste、Bernhard G. Steinmetz、Christopher Koradin
DOI:10.1002/chem.200401065
日期:2005.4.8
The Ru-catalyzed intramolecular [5+2] cycloaddition of cyclopropylenynes is investigated with respect to the regio- and diastereoselectivity as well as the functional group compatibility of the reaction. Evidence for the mechanism as occurring through a ruthenacyclopentene intermediate is elucidated from 1) the study of the diastereoselectivity of the cycloaddition; 2) the effect of variation of substituents
Ring-opening of some radicals containing the cyclopropylmethyl system
作者:Athelstan L. J. Beckwith、Graeme Moad
DOI:10.1039/p29800001473
日期:——
Mono- and bi-cyclic radicals containing the cyclopropylmethyl system are readily generated by interaction of the appropriate halides with triphenyl- or tributyl-stannane. Each radical studied underwent ring-opening by fission of the more substituted βγ-bond. In the case of the secondary radical (12b) the new double bond was formed preferentially in the trans-configuration. Rate constants, which cannot
通过适当的卤化物与三苯基或三丁基锡烷的相互作用,容易产生含有环丙基甲基系统的单环和双环基团。每个被研究的基团都通过更取代的βγ键的裂变而开环。在第二自由基(12b)的情况下,优先以反式构型形成新的双键。无法通过此方法高精度确定的速率常数在1×10 7 –3×10 8 s –1的范围内在25°C下。当通过流动方法在esr腔中产生时,α-羟基环丙基甲基自由基经历β裂变,随后进行1,5-氢原子转移以提供烯氧基。与非极性溶剂相比,后者在水中的反应更慢。刚性羟基降三环基自由基(43)可能会由于过渡态的偶极性质而优先发生取代度较低的βγ键的裂变。
Gold(I)-Catalyzed Ring Expansions of Unactivated Alkynylcyclopropanes to (<i>E</i>)-2-Alkylidenecyclobutanamines in the Presence of Sulfonamides
作者:Siyu Ye、Zhi-Xiang Yu
DOI:10.1021/ol9028786
日期:2010.2.19
The ringexpansion of cyclopropane derivatives provides a powerful method to construct synthetically useful four-membered carbocycles. Herein, a new type of gold(I)-catalyzed ringexpansion of an unactivated alkynylcyclopropane/sulfonamide trapping strategy to (E)-2-alkylidenecyclobutanamines was described. The reaction tolerates a range of aryl and alkyl substituents with moderate to good yields.
chlorine tocis-cyclooctene yields thetrans-dichloride, which has a dipole moment of 3·1D, that is slightly solvent dependent. The correspondingcis-dichloride was not obtained by the chlorination of thetrans-olefin, but was synthesized indirectly, and found to have a dipole moment of 2·3D, which is also solvent dependent. The addition of halogen totrans-cyclooctene was shown to yield a complex mixture of products