Transition Metal-Mediated Aromatic Ring Construction

TRANSITION METAL-MEDIATED AROMATIC RING CONSTRUCTION 

Department of Applied Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology, Meguro-ku, Tokyo, Japan 

Recent significant advance in the area of the transition metal-mediated aromatic ring construction reactions enables the construction of substituted benzenoid aromatic rings with efficient and convenient manners [1], These aromatic ring constrnction reactions provide promising new routes to the complex benzenoid aromatic compounds. In this chapter, I snmmarize the intermolecular multicomponent reactions and the intramolecnlar single-component reactions, which are able to construct benzenoid aromatic rings. 

As the intermolecular multicomponent reactions, three-component cycloaddition reactions (21.2 [2+2-1-2] cycloaddition and 21.3 [3+2+1] cycloaddition) and two-component cycloaddition reactions (21.4 [4+2] cycloaddition) are described. As the intramolecnlar single-component reactions, cycloaromatization reactions (21.5 intramolecular hydroarylation of alkynes and cychzation via transition metal vinybdenes) are described. Aromatic ring constrnction reactions involving aryne reactions (Chapter 12), rearrangement reactions (Chapters 16 and 18), metathesis reactions (Chapter 17), and coupling reactions (Chapters 19 and 20) are described in these different chapters. 

In 1948, Reppe reported the first example of the transition metal-catalyzed [2+2+2] cycloaddition of alkynes by using a nickel complex [2]. Vollhardt extensively studied utilization of the cobalt-mediated [2+2+2] cycloaddition in organic synthesis [3a, b], and Yamazaki studied general reactivity of 

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T. Matsuda, Synthesis of heterocycles via X—H bond addition to diynes. in Transition-Metal-Mediated Aromatic Ring Construction. (Ed K. Tanaka), p. 537. John Wiley Sons, Ltd., New York, 2013. 

TRANSITION METAL-MEDIATED AROMATIC RING CONSTRUCTION... 

In this chapter, the intermolecular multicomponent aromatic ring construction reactions and intramolecular single-component aromatic ring construction reactions are described. Among them, the [2+2+2] cycloaddition and intramolecular hydroarylation reactions are the most widely employed and reliable method. Various polycyclic and sterically hindered aromatic compounds have been synthesized by this method. In the past 10 years, the asymmetric [2+2+2] cycloaddition and intramolecular hydroarylation reactions have been developed, which enabled the enantioselec-tive synthesis of sterically hindered chiral aromatic compounds, such as axially chiral biaryls, planar chiral cyclophanes, and helically chiral heUcenes. Details of the transition metal-mediated aromatic ring construction reactions are comprehensively covered in the recently published book... 

Further development of efficient and powerful transition metal-mediated aromatic ring construction reactions would enable the more fadle and diverse synthesis of complex benzenoid aromatic compounds. 

For selected recent reviews, see (a) Hilt, G., Punner, F. (2013) Diels-Alder reactions. In Tanaka, K. (Ed.) Transition-Metal-Mediated Aromatic Ring Construction. John Wiley Sons, Hoboken, pp. 341-353. (b) Reymond, S., Cossy, J. (2008). Copper-catalyzed Diels-Alder reactions. Chemical Reviews, 108, 5359-5406. (c) Shen, J., Tan, C.-H. (2008). Br0nsted-acid and Brpnsted-base catalyzed Diels-Alder reactions. Organic Biomolecular Chemistry, 6, 3229-3236. 

Transition-Metal-Mediated Aromatic Ring Construction... 

Transition-Metal-Mediated Aromatic Ring Construction, First Edition. Edited by Ken Tanaka. 2013 John Wiley Sons, Inc. Published 2013 by John Wiley Sons, Inc. 

The transition-metal-mediated aromatic ring construction reaction via the [2 -I- 2 -I- 2] cycloaddition reaction is not restricted to the formation of a single benzene moiety. As already discussed within the intramolecular version of this reaction [i.e., the syntheses of (+)-viridin (47) and the angucyclines 58-60], this pivotal cycloaddition reaction can be used for the synthesis of naphthalene or anthracene moieties whenever it is embedded in a sequence of consecutive reactions. However, a more straightforward entry to the naphthalene core was realized during synthesis of the lignans taiwanin C (100) and E (101) (Scheme 7.21) [30]. 

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