Issue 15, 2014

Out-Basicity of 1,8-bis(dimethylamino)naphthalene: the experimental and theoretical challenge

Abstract

A possibility of non-conventional two-step protonation of 1,8-bis(dimethylamino)naphthalene (proton sponge) is discussed. Unlike the generally accepted mechanism, involving relatively slow direct penetration of a proton into the cleft between the peri-NMe2 groups, it consists of the rapid addition of a proton to the out-inverted NMe2 group with the subsequent slower rotational transfer of the proton into the inter-nitrogen space to produce a stable chelated cation. The following approaches were employed during the work: (1) competitive hydrogen bond formation in a specially designed alcohol in which the OH group might chelate either the proton sponge 1-NMe2 group or another basic center (N,N-dimethylaniline) of known basicity; (2) measuring the basicity of naphtho[1,8-b,c]diazabicyclo[3.3.3]undecane considered to be a close analogue of the proton sponge capable exclusively of out-protonation; (3) X-ray, spectral and DFT studies of structure, energy and stereodynamics of compounds obtained, including their conformers. For the first time, the pKa value of an organic base with a perfectly flat nitrogen atom is reported. The final conclusion is made that both pathways of proton sponge protonation, traditional and non-conventional, contribute in parallel with a still undefined ratio. The estimated out-basicity of the proton sponge is at least 5.5 orders of magnitude lower than the directly measured in-basicity.

Graphical abstract: Out-Basicity of 1,8-bis(dimethylamino)naphthalene: the experimental and theoretical challenge

Supplementary files

Article information

Article type
Paper
Submitted
03 Oct 2013
Accepted
19 Dec 2013
First published
20 Dec 2013

Org. Biomol. Chem., 2014,12, 2360-2369

Out-Basicity of 1,8-bis(dimethylamino)naphthalene: the experimental and theoretical challenge

V. A. Ozeryanskii, A. F. Pozharskii, A. S. Antonov and A. Filarowski, Org. Biomol. Chem., 2014, 12, 2360 DOI: 10.1039/C3OB41986J

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements