Ring Size and Substituent Effects in Oxyanion-Promoted Cyclizations of Enyne-allenes: Observation of a Myers−Saito Cycloaromatization at Cryogenic Temperature
摘要:
A series of acetoxy-substituted enyne-allenes, fused to cyclopentene and cyclohexene ring systems, were synthesized and treated with methyllithium to generate the corresponding enolates. It was found that whereas the cyclohexannulated examples underwent either C-2-C-7 (Myers-Saito) cycloaromatization or C-2-C-6 (Schmittel) cyclization depending on their terminal subsituents, the cyclopentannulated examples either failed to cyclize altogether or underwent C-2-C-7 cyclization. Both of these results lie in contrast to the behavior of their benzannulated analogues, which underwent exclusive C-2-C-6 cyclization independent of substituents. These findings are rationalized on the basis of both ring strain effects and the steric encumbrance of the terminal alkynyl and allenyl subsituents.
Nitromethane as a Carbanion Source for Domino Benzoannulation with Ynones: One‐Pot Synthesis of Polyfunctional Naphthalenes and a Total Synthesis of Macarpine
applicability has been devised for the regioselective synthesis of polyfunctional naphthalenes by employing nitromethane and ortho‐haloaryl ynones. Utilization of nitromethane as a one carbon carbanion source that is incorporated into a variety of ynones, ends up as an aromatic nitro substituent. The application of this domino process towards a total synthesis of the polycyclic alkaloid macarpine demonstrate
的单釜,过渡金属-自由,多米诺迈克尔/ S Ñ普遍适用性的Ar协议已经通过使用硝基甲烷和设计用于多官能萘的区域选择性合成邻-haloaryl ynones。硝基甲烷作为一种碳碳负离子源的使用,并被引入到各种炔酮中,最终以芳族硝基取代基的形式出现。该多米诺法在多环生物碱马卡平的全合成中的应用证明了该方法的有效性。在概念上是简单的方法来影响ynones显示广泛的底物范围和官能团耐受性,并已与被取代的硝基甲烷实现的区域选择性,多功能benzoannulation以及与脂环ö-单倍体。
Orthogonal Strapping of <i>o</i>-Haloaryl Ynones with Pyrazolones: A One-Pot, Domino Process toward Spiropyrazolones
作者:Mallesh Beesu、Goverdhan Mehta
DOI:10.1021/acs.joc.0c02087
日期:2020.11.6
assembled from diverse o-haloaryl ynones and β-bromoalkenyl ynones via base mediated, one-pot, metal free, orthogonal strapping (tethering) mediated by the recursive anion(s) derived from pyrazolones. These convenient, preparatively useful transformations proceed through either a tandem Michael addition–intramolecular SNArreaction or a tandem Michael addition–intramolecular AdNE process to furnish
通过由吡唑啉酮衍生的递归阴离子介导的碱介导的,一锅,无金属,正交捆扎(束缚),由多种邻卤代芳基炔酮和β-溴烯基炔酮组装而成了一类新型的螺旋形吡唑啉酮支架。这些方便,可用于制备的转化过程可通过串联的迈克尔加成-分子内S N Ar反应或串联的迈克尔加成-分子内Ad N E过程进行,以从易于获得的前体中提供多种药效学,多样的,螺旋形的吡唑啉酮。