carbonylation reaction for the synthesis of fluoren‐9‐ones from 2‐halogenated biphenyls using phenyl formate as a carbon monoxide surrogate was achieved. The combined use of cesium carbonate and o‐anisic acid resulted in a remarkable rate enhancement, where the reaction was complete within 3 min in some cases. Mechanistic studies indicated that the turnover‐limiting step of the reaction was the C−H bond‐cleaving
various biarylcarboxylic acids via photoredox catalysis. Attractive features of this process include generation of acyl radical, which quickly underdone intramolecular radical cyclization. This method marks the first photocatalytic intramolecular acyl radical coupling for constructing carbon–carbon bond, which further synthesizes the valuable fluorenone products with mild conditions, good yields, and
using a Pd(OAc)2/PCy3 system is described. A wide range of 2-arylbenzoyl fluoride derivatives can be used as fluorenone precursors and the reaction proceeds via an intramolecular coupling between aromatic C–H bonds with acyl C–F bonds. The reaction can be applied to the synthesis of indenofluorenedione derivatives and to the construction of other molecules with five-membered rings.
Direct Deoxygenative Intramolecular Acylation of Biarylcarboxylic Acids
作者:Chengjian Zhu、Jin Xie、Yantao Li、Wentao Xu
DOI:10.1055/s-0040-1707246
日期:2021.3
A photocatalyzed intramolecular cyclization is developed for the synthesis of fluorenones. In this photoredox reaction, triphenylphosphine is used as an inexpensive and effective deoxygenative reagent for biarylcarboxylic acids to give acyl radicals, which quickly undergo intramolecular radical cyclization. Reactions in the presence of air and continuous flow photoredox technology demonstrate the generality
Synthesis of highly substituted fluorenones via metal-free TBHP-promoted oxidative cyclization of 2-(aminomethyl)biphenyls. Application to the total synthesis of nobilone
作者:Ilya A P Jourjine、Lukas Zeisel、Jürgen Krauß、Franz Bracher
DOI:10.3762/bjoc.17.181
日期:——
Highlysubstituted fluorenones are readily prepared in mostly fair to good yields via metal- and additive-free TBHP-promoted cross-dehydrogenative coupling (CDC) of readily accessible N-methyl-2-(aminomethyl)biphenyls and 2-(aminomethyl)biphenyls. This methodology is compatible with numerous functional groups (methoxy, cyano, nitro, chloro, and SEM and TBS-protective groups for phenols) and was further
通过不含金属和添加剂的 TBHP 促进的易于获得的N-甲基-2-(氨甲基)联苯和 2-(氨甲基)联苯的交叉脱氢偶联 (CDC),可以轻松制备高度取代的芴酮,收率基本上相当到良好。该方法与多种官能团(甲氧基、氰基、硝基、氯以及苯酚的 SEM 和 TBS 保护基团)兼容,并进一步用于天然产物诺比隆的首次全合成。