Visible Light Mediated Decarboxylation And Cyclization To Synthesize Polysubstituted Pyridine Salts

With the development of a series of novel metal catalysts and organic dye catalysts,it has become one of the research hotspots in organic chemistry to apply visible light sources especially renewable and inexhaustible solar resources to excite organic molecules to achieve further transformation.In recent years,the visible-vight-excited decarboxylation has been a powerful synthesis method for the the formation of C-C and C-X(X=heteroatom)bonds.Because of its high efficiency and environment-friendly,visible-vight-excited decarboxylation has been widely concerned and developed rapidly.This paper introduces the research progress in this field,and the research related to photocatalysis decarboxylation we have developed.Amino acids and their derivatives are abundant and inexpensive,and their conversion into high-value products by decarboxylative coupling reactions include the formation of C-C and C-X(X=heteroatom)bonds represents an important goal.In this dissertation we have developed a photoinduced decarboxylative 1,6-annulation under the irradiation of 23 W CFL(Compact Fluorescent Lamp)using proline derivatives and phenylacetaldehyde as the starting material and photoexcited precursors.The reaction can be excited by visible light at room temperature in air to achieve the construction of the multi substituted pyridine salts.With the reasearch on mechanism and Uv-vis absorption experiment,we proposed a plausible mechanism: the color imide intermediate could be obtained through the dehydration condensation of proline and the aldol reaction condensation product of phenylacetaldehyde.This color imide intermediate,as the photosensitizer in the process of photocatalysis,occurs an electron transfer reaction,then realizes a decarboxylative 1,6 cyclization in air to obtain multisubstituted pyridine salts.This photochemical reaction does not require the use of any additional transition metal catalyst and organic dye catalyst which is mild and green.Our development of photocatalytic decarboxylative 1,6 cyclization can make use of the optical properties of the color imide intermediate,without the addition of any additional transition metal catalyst and organic dye catalyst.The method developed a new method and perspective for the synthesis of various pyridine salts.The photocatalytic decarboxylative 1,6 cyclization can be occured at ambient air and rom temperature with the most common light source.A series of pyridine salts were synthesized by constructing three carbon carbon bond and a pyridine ring via this photochemical cyclization.These pyridine compounds are important structural features of natural products and pharmaceuticals,and some of them are the indole quinazoline alkaloids.