Metal-mediated synthesis of furans and pyrroles

Nitin T Patil,Yoshinori Yamamoto,Girolamo Cirrincione

doi:10.3998/ark.5550190.0008.a11

Abstract

The transition metal catalyzed synthesis of furans and pyrroles is becoming an important and highly rewarding protocol in organic synthesis. This review focuses on the use of transition metal as a catalyst for the synthesis of furans and pyrroles along with their interesting mechanistic aspects. The synthetic efforts in this area will clearly culminate in tackling the major issues pertaining to atom economy and environmentally acceptable technologies for future.

Highlights

Substituted furans[1] and pyrroles[2] are a structural component of a vast number of biologically active natural and unnatural compounds
Synthesis of them has been the objective of research for over a century, and a variety of well-established classical methods are available in the literature.[3]
The formation of furans and pyrroles by using various transition metals has been investigated in the literature

Summary

Introduction

Substituted furans[1] and pyrroles[2] are a structural component of a vast number of biologically active natural and unnatural compounds. Either the AuCl3 activates the enones 4 to form 8, which create the new C-C bonds by an electrophilic aromatic substitution at the 5-position of the furan to provide 7 (path A), or a cyclization of 3 under gold catalysis forms a furyl–gold species 6, which subsequently undergoes a 1,4-addition to the Michael acceptor (path B). Gevorgyan et al have shown that 1,2-iodine, -bromine, and -chlorine migration in haloallenyl ketones 9 takes place in the presence of AuCl3.8 For this reaction iodo and bromo allenyl ketones gave best results, compared to their chloro analogue. This chemistry is interesting as a novel cascade transformation and serves as a mild, selective, and efficient approach to different types of 3-halofurans 10. It is interesting to note that just by switching solvent from toluene to THF caused a dramatic change in selectivity affording 2-bromofurans as the major product

12 O R3 AuLn

H H C4H9