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Negishi Coupling for Highly Selective Syntheses of Allenes via Ligand Effect and Mechanistic Study via SAESI‐MS/MS
Author(s) -
Zheng Yangguangyan,
Miao Bukeyan,
Qin Anni,
Xiao Junzhe,
Liu Qi,
Li Gen,
Zhang Li,
Zhang Fang,
Guo Yinlong,
Ma Shengming
Publication year - 2019
Publication title -
chinese journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.28
H-Index - 41
eISSN - 1614-7065
pISSN - 1001-604X
DOI - 10.1002/cjoc.201900322
Subject(s) - chemistry , negishi coupling , allene , ligand (biochemistry) , catalytic cycle , reactivity (psychology) , catalysis , combinatorial chemistry , selectivity , medicinal chemistry , stereochemistry , organic chemistry , medicine , biochemistry , receptor , alternative medicine , pathology
Summary of main observation and conclusion β‐H elimination is an intrinsic problem in transition metal‐catalyzed reactions. We describe herein an interesting ligand effect for Et 2 Zn acting as either ethyl provider or H provider, respectively: by applying SPhos or Gorlos‐Phos as the ligand, β‐H elimination has been successfully controlled in the corresponding Negishi coupling reaction affording different poly‐substituted allenes in good yields and excellent selectivities. SAESI‐MS ( S olvent A ssisted E lectrospray I onization M ass S pectrometry) has been applied to successfully capture the highly reactive organometallic intermediates, which show the different coordination behaviors of Pd with SPhos or Gorlos‐Phos as the ligand in the catalytic cycle. In addition, the different reactivities of Int 1 and Int 2 towards the formation of the final allene products have been demonstrated via SAESI‐MS/MS experiments. These MS studies visualized the whole catalytic cycle for the Negishi coupling reaction while nicely explain the observed reactivity and selectivity.