Allylated β-Ketoesters as Precursors in Paal-Knorr-Type Pyrrole Synthesis: Preparations of Chiral and Bispyrroles

Abstract

A simple and facile preparation of chiral and bis-pyrroles is described here. This method involves a modified Paal-Knorr reaction using 1,4-dicarbonyl systems derived from ozonolysis of allylated b-ketoester.

Three-component reactions of aromatic amines, 1,3-dicarbonyl compounds, and α-bromoacetaldehyde acetal to access N-(hetero)aryl-4,5-unsubstituted pyrroles

“…α,β-Unsaturated aldehydes have also been used as the C 3 donor to construct pyrrole scaffolds [27,28]; (ii) [1 + 4] annulation, in which (hetero)arylamines are reacted with a C 4 donor to form the pyrrole ring; many functional molecules, such as bioderived furans [29], (Z)-enynols [30], 1-vinylpropargyl alcohols [31], doubly activated cyclopropanes [32], and enynals [33], can be used as C 4 counter reagents. The carbon-based 1,4-biselectrophiles, such as the 1,4-dicarbonyl compounds [34,35], γ-car-bonyl tert-butyl peroxides [36], and dihydrofurans [37] have also been reported to construct the pyrrole skeletons through this type of annulation; and (iii) [1 + 2 + 2] annulation, in which (hetero)arylamines are reacted with two different molecules, and each of them contributes two carbon atoms to construct a pyrrole ring [38][39][40][41][42]. Among these three approaches, the third is considered the most attractive route for N-(hetero)aryl-4,5-unsubstituted pyrrole synthesis.…”