TY - JOUR

T1 - Unusual temperature-sensitive protonation behaviour of 4-(dimethylamino)pyridine

AU - Genaev, Alexander M.

AU - Salnikov, George E.

AU - Koltunov, Konstantin Yu

N1 - Funding Information: This work was conducted within the framework of the budget projects for Vorozhtsov Novosibirsk Institute of Organic Chemistry (No. AAAA-A18-118020290191-2) and Boreskov Institute of Catalysis (No. AAAA-A17-117041710083-5) supported by the Ministry of Science and Higher Education of the Russian Federation. We also acknowledge the Multi-Access Chemical Research Center of the Siberian Branch of the Russian Academy of Sciences for the spectral measurements and the Cluster of the Information Computation Center, Novosibirsk State University (http://www.nusc.ru/) for computing resources. Publisher Copyright: © The Royal Society of Chemistry 2021. Copyright: Copyright 2021 Elsevier B.V., All rights reserved.

PY - 2021/1/28

Y1 - 2021/1/28

N2 - Stimuli-responsive and, in particular, temperature-responsive smart materials have recently gained much attention in a variety of applications. On the other hand, 4-(dimethylamino)pyridine (DMAP) and related structures are widely used as nucleophilic catalysts and also as specific parts of rationally designed molecules, where reversible reactions of the pyridinic nitrogen with electrophiles are involved. In our study, we have found an unexpectedly significant impact of temperature on the protonation degree of DMAP derivatives, especially in the case of protonation of the 4-(dimethylamino)-1-(2,3,5,6-tetrafluoropyridin-4-yl)pyridinium cation, derived from the reaction of DMAP with pentafluoropyridine. Thus, when dissolved in the TfOH-SO2ClF-CD2Cl2acid system at 30 °C, this cation underwent a slight (<7%) protonation on the dimethylamino group, while the temperature decrease to −70 °C resulted in its complete protonation. Notably, such a scale of this phenomenon has never been observed before for other weak nucleophiles, being many times lower at the same change of temperature. The mechanistic aspects of these intriguing results are discussed.

AB - Stimuli-responsive and, in particular, temperature-responsive smart materials have recently gained much attention in a variety of applications. On the other hand, 4-(dimethylamino)pyridine (DMAP) and related structures are widely used as nucleophilic catalysts and also as specific parts of rationally designed molecules, where reversible reactions of the pyridinic nitrogen with electrophiles are involved. In our study, we have found an unexpectedly significant impact of temperature on the protonation degree of DMAP derivatives, especially in the case of protonation of the 4-(dimethylamino)-1-(2,3,5,6-tetrafluoropyridin-4-yl)pyridinium cation, derived from the reaction of DMAP with pentafluoropyridine. Thus, when dissolved in the TfOH-SO2ClF-CD2Cl2acid system at 30 °C, this cation underwent a slight (<7%) protonation on the dimethylamino group, while the temperature decrease to −70 °C resulted in its complete protonation. Notably, such a scale of this phenomenon has never been observed before for other weak nucleophiles, being many times lower at the same change of temperature. The mechanistic aspects of these intriguing results are discussed.

UR - http://www.scopus.com/inward/record.url?scp=85100392285&partnerID=8YFLogxK

U2 - 10.1039/d0ob01893g

DO - 10.1039/d0ob01893g

M3 - Article

C2 - 33409515

AN - SCOPUS:85100392285

VL - 19

SP - 866

EP - 872

JO - Organic and Biomolecular Chemistry

JF - Organic and Biomolecular Chemistry

SN - 1477-0520

IS - 4

ER -