Cationic Rhodium(I)/BINAP-Type Bisphosphine Complexes: Versatile New Catalysts for Highly Chemo-, Regio-, and Enantioselective [2+2+2] Cycloadditions

Abstract

Our research group was the first to discover that cationic rhodium(I)/BINAP-type bisphosphine complexes are versatile new catalysts for highly chemo-, regio-, and enantioselective [2+2+2] cycloadditions. The high chemo- and regioselectivity of these ­cycloadditions enabled efficient catalytic synthesis of substituted benzenes, cyclophanes, and nitrogen heterocycles. Furthermore, enantioselective variants of these cycloadditions were also developed that realized efficient catalytic constructions of axial, planar, central, and spiro chirality.

1 Introduction

2 Chemo- and Regioselective [2+2+2] Cycloadditions

2.1 [2+2+2] Cycloaddition of Terminal Alkynes

2.2 [2+2+2] Cycloaddition of Two Different Alkynes

2.3 [2+2+2] Cycloaddition of α,ω-Diynes with Alkynes

2.4 [2+2+2] Cycloaddition of Alkynes with Isocyanates, Isothiocyanates, and Carbon Disulfide

2.5 [2+2+2] Cycloaddition of Alkynes with Nitriles

3 Enantioselective [2+2+2] Cycloadditions

3.1 Construction of Axial Chirality

3.2 Construction of Planar Chirality

3.3 Construction of Central Chirality

3.4 Construction of Spiro Chirality

4 Summary

Key words

alkynes - asymmetric catalysis - BINAP - cycloadditions - rhodium

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49

For RhCl(PPh₃)₃-catalyzed [2+2+2] cycloadditions involving alkynamides, see refs 11h, 11i, and 11q.

59

For rhodium-catalyzed macrocyclizations to form ortho- and metacyclophanes via intramolecular [2+2+2] cycloaddition of triynes in an aqueous-organic biphasic system, see reference 11n.

62

For examples of transesterification in metal-catalyzed [2+2+2] cycloadditions, see references 19c, 19e, and 19f.

65

For the synthesis of chiral phthalides by RhCl(PPh₃)₃-catalyzed [2+2+2] cycloadditions of ester-linked diynes with acetylene, see references 11k and 11l.