10.1002/anie.202010251
Angewandte Chemie International Edition
COMMUNICATION
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Considering that aryl ethers or aryl fluorides are effective, the
reaction with aryl electrophiles would proceed through an ionic
SNAr mechanism. However, the reaction with aryl nitriles gave
the low yield and the small amount of homo-coupled product
which stems from tertiary benzylboronate was detected. Thus,
the reaction pathway of aryl nitriles would be contaminated with
a radical SNAr mechanism involving a single electron transfer
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[8] In some cases, deborylprotonated product was detected.
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deborylprotonated product. When PhLi was used instead of KOtBu on the
reaction between (R)-1a and 2a, a complete loss of chirality in 3aa was
observed
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In summary, a transition-metal-free cross-coupling reaction for
the construction of quaternary carbon centers from tertiary
benzylboronates has been demonstrated. The protocol enabled
the use of alkyl or aryl electrophiles. Thus, this transformation
has expanded the scope of tertiary alkylative cross-coupling
using organoboronates. The reaction involves the generation of
tertiary alkyl anions from organoboronates in the presence of an
alkoxide base followed by their substitution reactions. Extending
the scope of this reaction to electrophiles is in progress.
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This work was supported by JSPS KAKENHI Grant Number
JP18H01971 (Scientific Research (B)), JP17H06449 (Hybrid
Catalysis), and JP20J20600 (JSPS Fellows) as well as JST,
PRESTO Grant Number JPMJPR19T2.
Keywords: cross-coupling
·
tertiary alkylation
·
tertiary
alkylboronate · quaternary carbon center · transition-metal-free
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