Easily Prepared Azopyridines As Potent and Recyclable Reagents for Facile Esterification Reactions. An Efficient Modified Mitsunobu Reaction

Abstract

The 2,2'-, 3,3'-, and 4,4'-azopyridines (azpy) and their alkyl pyridinium ionic liquids were studied as a new class of electron-deficient reagents for Mitsunobu esterification reactions. Among these compounds, 4,4'-azopyridine was found to be the most suitable one for esterification and thioesterification reactions. This new reagent promises to provide general and complementary solutions for separation problems in Mitsunobu reactions without restricting the reaction scope and facilitates the isolation of its hydrazine byproduct. The pyridine hydrazine byproduct can be simply recycled to its azopyridine by an oxidation reaction.

Crystal Engineering with Iodoethynylnitrobenzenes: A Group of Highly Effective Halogen-Bond Donors

“…Iodoethynylnitrobenzenes, bromoethynylnitrobenzenes and chloroethynylnitrobenzenes were synthesized according to literature procedures. 37,38 A8 -A10 and A13 -A15 were synthesized following previously reported procedures, 39 as were A7 40 and A12. 41 Infrared spectra were recorded with a Nicolet 380 FT-IR.…”

Organocatalytic Mitsunobu Reactions with 3,5-Dinitrobenzoic Acid

“…For example, polystyrene-supported, 9 polymerizable, 10 acid-labile, 11 fluorous-tagged, 12 cyclodextrin-binding, 13 and phosphonium ion functionalized 14 analogues of 2 have been reported to simplify Mitsunobu reaction product purification. More recently, the use of di(4-chlorobenzyl) ester 5, 15 di(2-methoxyethyl) ester 6, 16 and azopyridine 7 17 have also been described in this context ( Figure 1). …”

Synthesis of Thioesters by Simultaneous Activation of Carboxylic Acids and Alcohols Using PPh3/NBS with Benzyltriethylammonium Tetrathiomolybdate as the Sulfur Transfer Reagent

“…The combined extract was evaporated, and the residue was purified by column chromatography on silica gel to give 30 as a colorless liquid (0.237 g, 70 % [20] 9, [21] 11, [22] 12, [23] 13, [24] 14, [25] 16, [26] 20, [27] and 22 [28] are reported, their 1 H NMR spectra are attached for confirmation.…”