Coumarin as a Surrogate for the Protection-group-free Synthesis of o-Hydroxy Stilbenes: Hydrolysis-Decarboxylation-Heck Coupling Reactions in One Pot.

The 2-hydroxystyrylbenzene scaffold is found in various compounds that are widely applicable in medicinal chemistry as well as material chemistry. Here, a successful attempt is made to develop a one-pot protocol for the synthesis of 2-hydroxystilbene derivatives via hydrolysis of natural coumarins followed by in situ decarboxylative Heck coupling with haloarenes. Fine tuning of the reaction conditions allowed exclusive formation of 2-hydroxystyrylbenzenes over other possible side products, i. e., benzofuran/substituted coumarins.

Thiol-ene "click" reaction triggered by neutral ionic liquid: the "ambiphilic" character of [hmim]Br in the regioselective nucleophilic hydrothiolation.

Thiol-ene "click" chemistry has emerged as a powerful strategy to construct carbon-heteroatom (C-S) bonds, which generally results in the formation of two regioisomers. To this end, the neutral ionic liquid [hmim]Br has been explored as a solvent cum catalyst for the synthesis of linear thioethers from activated and inactivated styrene derivatives or secondary benzyl alcohols and thiols without the requirement of using a metal complex, base, or free radical initiator. Furthermore, detailed mechanistic investigations using (1)H NMR spectroscopy and quadrupole time-of-flight electrospray ionization mass spectrometry (Q-TOF ESI-MS) revealed that the "ambiphilic" character of the ionic liquid promotes the nucleophilic addition of thiol to styrene through an anti-Markovnikov pathway. The catalyst recyclability and the extension of the methodology for thiol-yne click chemistry are additional benefits. A competitive study among thiophenol, styrene, and phenyl acetylene revealed that the rate of reaction is in the order of thiol-yne>thiol-ene>dimerization of thiol in [hmim]Br.