Synthesis and Characterization of Biguanide and Biguanidium Surfactants for Efficient and Recyclable Application in the Suzuki–Miyaura Reaction

Abstract

We report here the synthesis and thorough characterization of a new family of alkylbiguanides and alkylbiguanidium chlorides by 1 H and 13 C NMR and X-ray diffraction. Their critical micelle concentration was first determined by surface tension measurements. Hexylbiguanide was then studied as a surfactant in the micellar Suzuki–Miyaura cross-coupling reaction. The unexpected low reactivity of the system at high Pd/hexylbiguanide ratios was due to the change of the size and the shape of the aggregates, observed by transmission electron microscopy. The best catalytic activity was obtained for a 1:1 Pd/hexylbiguanide ratio for which the micellar conditions were conserved. Better results were obtained for several substrates, when compared to those previously obtained with metformin under the same reaction conditions. Higher yields and a better recyclability were obtained under micellar conditions with hexylbiguanide.

Ligand Steric Effects of α-Diimine Nickel(II) and Palladium(II) Complexes in the Suzuki–Miyaura Cross-Coupling Reaction

“…Notably, Ni B and Pd B afforded more than 90% yields for unsubstituted biaryl compounds 1A2 and 2A1 synthesized from phenylboronic acid and 2-naphthylboronic acid, respectively, whereas a catalytic system comprising hexylbiguanide as a free ligand and commercially available palladium(II) acetate presented only 22% yield. 13 In OLED application, anthracene is an essential structural motif that contributes strong blue electroluminescence associated with a low electronic band gap. 89 In this interest, both sterically hindered 9,10-dibromoanthracene and 2-naphthylboronic acid were successfully coupled for generating 2A4 , maintaining a comparable yield to 1A9 ( Schemes 2 and 3 ) regardless of the steric difference.…”

Mild Biamidine-Transfer Conditions for the Synthesis of Aliphatic Biguanides

“…8,9 Nevertheless, conditions remain harsh and prolonged heating is still necessary. 10,11 Alternatively, the pre-activation of cyanoguanidine has been described through the use of N-(diaminomethylene)-1H-pyrazole-1-carboximidamide hydrochloride (1a) 2,[12][13][14][15][16] or S-methylguanylisothiouronium iodide (1b) 2,17 as biamidine transfer reagents. However, these conditions suffer from low to moderate isolation yields, long reaction times and/or harsh conditions.…”

Efficient N-formylation of primary aromatic amines using novel solid acid magnetic nanocatalyst

“…2). 35,36 The regular acid catalysts includes mineral acids viz. H 2 SO 4 , HCl, HF and other organic acids like p-toluene sulfonic acid, leading to severe disadvantages like corrosion, toxicity, tedious separation of catalysts from homogeneous reaction mixtures and urgency of neutralization of waste streams.…”