Synlett 2020; 31(13): 1259-1267
DOI: 10.1055/s-0040-1707962
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© Georg Thieme Verlag Stuttgart · New York

Relevance of the Entropy Factor in Stereoselectivity Control of Asymmetric Photoreactions

Tadashi Mori
Financial support from the Japan Society for the Promotion of Science [Grant-in-Aid for Scientific Research, Challenging Exploratory Research, Promotion of Joint International Research (Fostering Joint International Research) (Grant Nos. JP16H06041, JP16KK0111, JP17H05261, JP18K19077, and JP18H01964)], the Asahi Glass Foundation, the Murata Science Foundation, the Tonen General Sekiyu Research/Development Encouragement & Scholarship Foundation, and the Cooperative Research Program of the Network Joint Research Center for Materials and Devices is greatly acknowledged.
Further Information

Publication History

Received: 19 February 2020

Accepted after revision: 11 March 2020

Publication Date:
24 April 2020 (online)


This paper is dedicated to the memory of the late Professor Rajendra Rathore, Marquette University and the late Professor Jay K. Kochi, Houston University.

Abstract

Entropy as well as enthalpy factors play substantial roles in various chemical phenomena such as equilibrium and reactions. However, the entropy factors are frequently underestimated in most instances, particularly in synthetic chemistry. In reality, the entropy factor can be in competition with the enthalpy factor or can even be decisive in determining the overall free or activation energy change upon molecular interaction and chemical transformation, particularly where weak interactions in ground and/or excited states are significant. In this account, we overview the importance of the entropy factor in various chemical phenomena in both thermodynamics and kinetics and in the ground and excited states. It is immediately apparent that many diastereo- and enantioselective photoreactions are entropy-controlled. Recent advances on the entropy-control concept in asymmetric photoreactions are further discussed. Understanding the entropy-control concept will pave the way to improve, fine-tune, and even invert the chemo- and stereoselectivity of relevant chemical phenomena.

1 Introduction

2 Role of Entropy in Supramolecular Interactions

3 Selected Examples of Entropy-Driven Thermal Reactions

4 Classical Examples of Entropy Control in Photoreactions

5 Entropy-Driven Asymmetric Photoreactions

6 Advances in Entropy Control

7 Perspective