Special Issue Celebrating 40 Years of the Mukaiyama Aldol Reaction: Introductory Remarks

Abstract

The year 2013 marked the 40th anniversary of the Mukaiyama aldol reaction. In 1973, Mukaiyama, Narasaka, and Banno discovered a conceptually new C–C bond-forming reaction mediated by a Lewis acid, and published the groundbreaking report in the second volume of Chemistry Letters,1 the society journal for communications published by The Chemical Society of Japan. The reaction is an aldol reaction using silyl enol ethers as the nucleophile and titanium tetrachloride as the mediator. Now it has become one of the most useful C–C bond-forming methods, being known as the Mukaiyama aldol reaction. An aldol reaction is the vital C–C bond-forming reaction occurring in vivo. Aldolases synthesize poly-oxygenated compounds of complex structures with strict control of a variety of selectivities. On the other hand, it was not easy to carry out a directed cross aldol reaction in a flask until Mukaiyama disclosed the new aldol reaction using silyl enol ethers in 1973. Interestingly enough, it was also 1973 when House et al. reported a directed cross aldol reaction using lithium enolates.2 The two directed cross aldol reactions, which appeared in the same year of 1973, were contrasting in the reaction conditions, one under acidic and the other under basic conditions. Nonetheless, their impact was so immense that the augmented utility of the aldol reactions became widely recognized across the community of organic chemistry. These directed cross aldol reactions found a number of successful applications to natural product synthesis. In addition, the Mukaiyama aldol reaction provided a leading example of utilization of electron-rich but weak carbon nucleophiles in combination with Lewis acids, and the development of Danishefsky's diene chemistry3 and the Hosomi/Sakurai reaction4 immediately followed. The Mukaiyama aldol reaction also induced the rise of chemistry of stereoselective C–C bond formation and Lewis acid catalysis for asymmetric synthesis, which were the major issues in organic synthesis in the 1980s and 1990s. With these illuminating backgrounds, the Mukaiyama aldol reaction was celebrated in various ways on the occasion of its 40th anniversary. This special issue is one of them. Angewandte Chemie placed three review articles back-to-back, which overviewed the chemistry as well as the history related to the Mukaiyama aldol reaction.5-7 On August 31, 2013, a symposium celebrating the 40th anniversary was held in Tokyo, collecting 500 participants.8 It was organized by the academic progeny of Mukaiyama in order to honor his outstanding contribution to the field of organic synthesis. Those in academia that Mukaiyama has directly supervised amount to well over 50, including Mitsunobu from his time at Gakushuin University. They all learned a lot from his mentorship in scientific, professional, and personal standpoints. Their gratefulness to Mukaiyama's mentorship manifests itself in this special issue, which is authored by several of his progeny. I wish to describe another admirable contribution of Mukaiyama to end up my introductory remarks. Japan hosted the first Tokyo Olympic games in 1964 (and will host again in 2020). It greatly encouraged Japan nationwide to recover from the devastation caused by World War II. The chemistry community also tried to re-establish itself on its own by launching a new society journal for communications. That was Chemistry Letters, which was launched in 1972. However, the situation at the time could be described as helpless and dire. The first editor-in-chief of Chemistry Letters, Goto, mentioned at the launch that it would require much efforts and endurance of the members, as well as a long time, to nurture this journal. Mukaiyama immediately started publishing his new research results in Chemistry Letters on an exclusive basis. His publications in Chemistry Letters amounted to over 600 when he retired from research in 2008, and as a result, greatly promoted its subscription at overseas libraries. Now Chemistry Letters has become globally recognized as an international journal from Japan. Mukaiyama became instrumental again later in his career in launching another society journal from Japan. He took the inaugural editorship of a unique review journal, The Chemical Record, on his shoulders in 2001 and set it on an excellent path to international prominence. It is thus very fitting that we can celebrate the 40th anniversary of the Mukaiyama aldol reaction with this special issue. There have recently been so many arguments protesting against bibliometrics and sky-rocketing costs for libraries.9 “We should liberate our minds again to enable true creativity in view of long-term social benefits.” A Nobel Prize laureate, Richard Ernst, warned us with such strong words.10 I believe we can find the simplest, plainest, but most straightforward, most clear-cut, and perhaps most effective solution in Mukaiyama's determined life-long faithful consecration to our society journals. Masahiro Murakami Kyoto University This preface is dedicated to Mrs. Hiroko Mukaiyama, Prof. Mukaiyama's beloved wife who devoted her life to him.