Beilstein J. Org. Chem.2021,17, 203–209, doi:10.3762/bjoc.17.20
resulted in safer procedures for the preparation of 2H-azirines, offering valuable alternatives for production purposes. In 2013, Kirschning harnessed the photoinduced electrocyclization of vinyl azides in a microfluidicphotoreactor yielding 2H-azirines as precursors of 1,3-dipolarophiles (Scheme 1a) [27
]. Similarly, Maurya developed a microfluidicphotoreactor for the synthesis of a fused β-carboline from an α-ketovinyl azide and a 1,2,3,4-tetrahydro-β-carboline (Scheme 1b) [30]. More recently, Kappe reported the generation of 2H-azirines under continuous flow conditions, and their transformation into
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Graphical Abstract
Scheme 1:
Flow generation and transformation of 2H-azirines.
Beilstein J. Org. Chem.2018,14, 2418–2424, doi:10.3762/bjoc.14.219
synthetic method for the direct assembly of highly functionalized tetracyclic pharmacophoric cores. Coumarins and chromones undergo diastereoselective [4 + 2] cycloaddition reactions with light-generated photoenol intermediates. The reactions occur by aid of a microfluidicphotoreactor (MFP) in high yield
molecules.
Keywords: [4 + 2] photoenol; cycloaddition; flow chemistry; microfluidicphotoreactor; photoredox catalysis; synthetic photochemistry; Introduction
In recent years synthetic photochemistry has become highly sophisticated [1]. The opportunity of using renewable energy sources to transform and
functionalize organic molecules is receiving considerable interest from the scientific community [2]. Thus, innovative light-driven metal-free synthetic methods have been successfully developed [3]. More recently, the microfluidicphotoreactor (MFP) technology has revealed to be a key technology applicable for
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Graphical Abstract
Figure 1:
a) Light-driven reaction between 2-MBP A and maleimide B for the synthesis of C through a [4 + 2] c...