Journal
ORGANIC & BIOMOLECULAR CHEMISTRY
Volume 20, Issue 22, Pages 4559-4568Publisher
ROYAL SOC CHEMISTRY
DOI: 10.1039/d2ob00674j
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- Russian Science Foundation [20-73-00111]
- Russian Science Foundation [20-73-00111] Funding Source: Russian Science Foundation
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Selective heterocyclization leading to 1,2,3,4-tetrahydrobenzo[h]quinazolines from ortho-ketimines of 1,8-bis(dimethylamino)naphthalene (Dmanlms) under acid catalysis has been revealed. The reactivity difference between Dmanlms and N,N-dimethylaniline ortho-ketimine highlights the importance of the second peri-NMe2 group in Dmanlms.
Selective heterocyclization leading to 1,2,3,4-tetrahydrobenzo[h]quinazolines from ortho-ketimines of 1,8-bis(dimethylamino)naphthalene (Dmanlms) under acid catalysis has been revealed. In contrast to the rather unreactive N,N-dimethylaniline ortho-ketimine, Dmanlms readily undergo this transformation without an additional catalyst. This distinction in the reactivity underscores the importance of the second peri-NMe2 group in Dmanlms, which facilitates a [1,5]-hydride shift and the subsequent cyclization. The cascade of pen-interactions emerging between 1-NMe2 and 8-NMe2 groups has been identified as a reason for the catalytic effect: (1) the hydrogen bond in the Dmanlm dication constrains 1-NMe2 in the desired position providing proximity of reaction centers, (2) the repulsion of the lone pairs of 8-NMe2 group and unrelaxed 1-NMe2 group arising right after deprotonation process reduces the Gibbs free energy of activation (Delta G(double dagger)) for the straight hydride shift, and (3) the electrostatic interaction between 8-NMe2 and the charged N=CH2+ group in the intermediate increases the Delta G(double dagger) for the reverse hydride shift.
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