Magnesium-Mediated Carbon−Carbon Bond Formation in Aqueous Media:  Barbier−Grignard Allylation and Pinacol Coupling of Aldehydes

Abstract

Magnesium-mediated Barbier-Grignard type alkylation of aldehydes with alkyl halides was studied in aqueous media. The reaction of aromatic aldehydes with allyl halides is highly effective with either THF or water as the reaction solvent but poor in a mixture of THF/water. It was found that the magnesium-mediated allylation of aldehydes with allyl bromide and iodide proceeds effectively in aqueous 0.1 N HCl or 0.1 N NH(4)Cl. Aromatic aldehydes reacted chemoselectively in the presence of aliphatic aldehydes. An exclusive selectivity was also observed when both aliphatic and aromatic aldehyde functionalities are present in the same molecule. In the absence of allyl halides, aldehydes and ketones reacted with magnesium in aqueous 0.1 N NH(4)Cl to form the corresponding pinacol coupling products in high yields. The effectiveness of the pinacol reaction was strongly influenced by the steric environment surrounding the carbonyl group. Aliphatic aldehydes and simple alkyl halides appear inert under the reaction conditions for either alkylation or the pinacol coupling reaction.

An Original On‐Column Oxidative Cleavage of Vicinal Diols Using Alumina/Potassium Periodate: Application to Sequential Oxidation/Horner–Emmons Reactions

“…[25] The mixtures of cis/trans isomers are subjected to glycolic cleavage reactions without separation. [26] To a stirred suspension of acenaphthylene-1,2-dione (3.0 g, 16.5 mmoL) in methanol (50 mL), was added sodium borohydride (1.25 g, 32.9 mmol) in small portions at 0°C.…”

Synthesis of homoallylic amines and acylhydrazides by tin powder‐promoted multicomponent one‐pot allylation reactions

“…[9][10][11][12][13][14][15][16][17][18][19][20][21] As reported in the literature, allylic organometallics such as allylic Mg, [22,23] Zn, [24,25] In, [26][27][28][29] Sn, [30][31][32][33][34][35][36][37][38] Si, [39,40] B [25,41] and Sm [42,43] have been intensively investigated in allylation reactions. Among these organometallics, allylic stannanes have been widely used because of their easy availability, air and moisture stability, tolerance to functional groups and high selectivity.…”

Reduction and coupling reaction of carbonyl compounds by KI/Fe(OH)3in aqueous media

“…Recently, all pinacol coupling reactions in aqueous media required metal reduction of carbonyl compounds, by usage of Ti (12), Cu-Zn (13,14), Al (15,16), Mn (17), In (18), Mg (19), Ga (20), or Sm (21,22), affording inter-or intramolecular coupling products of carbonyl compounds. These reactions produced metal ion and even heavy metal ion with the potential to harm the environment.…”