Rasta resin–triphenylphosphine oxides and their use as recyclable heterogeneous reagent precursors in halogenation reactions

Abstract

SummaryHeterogeneous polymer-supported triphenylphosphine oxides based on the rasta resin architecture have been synthesized, and applied as reagent precursors in a wide range of halogenation reactions. The rasta resin–triphenylphosphine oxides were reacted with either oxalyl chloride or oxalyl bromide to form the corresponding halophosphonium salts, and these in turn were reacted with alcohols, aldehydes, aziridines and epoxides to form halogenated products in high yields after simple purification. The polymer-supported triphenylphosphine oxides formed as a byproduct during these reactions could be recovered and reused numerous times with no appreciable decrease in reactivity.

Merging shuttle reactions and paired electrolysis for reversible vicinal dihalogenations

“…The 1,2-dichloride compound 52, bearing a reactive benzylic tertiary C−Cl bond, was prepared in good yield from α-methylstyrene. Several other activated alkenes, such as the silyl-and ester-substituted alkenes, also proved to be viable substrates to deliver the dichloride products (53)(54)(55)(56), in particular, methyl cinnamate was converted to the 1,2-dichloride 56 in an excellent d.r. ratio (> 19:1).…”

Matsuda–Heck Arylation of Glycals for the Stereoselective Synthesis of Aryl C-Glycosides

“…7 We concluded our investigation into desoxy aryl-C-glycoside syntheses based on Matsuda− Heck reactions with the synthesis of a hitherto unknown α-6-desoxygliflozin 25. The required 3-benzylarene diazonium salt 22 was synthesized in four steps from commercially available benzyl alcohol 17, which was converted to the benzyl bromide 18 87 using Appel conditions (Scheme 5). As the next step for the generation of the diarylmethane 20, a Suzuki−Miyaura coupling of benzyl bromide 18 and boronic acid 19 was envisaged.…”

“…(3-Nitrophenyl)-methylbromide (18). 87 To a solution of (3nitrophenyl)-methanol 17 (3.83 g, 25.0 mmol) in CH 2 Cl 2 (40 mL) was added CBr 4 (10.78 g, 32.5 mmol), and the solution was cooled to 0 °C. PPh 3 (11.80 g, 45.0 mmol) was added in portions, and the solution was stirred for 4 h. The solvent was reduced in vacuo to approximately 10 mL, and the mixture was filtered through celite and washed with diethylether.…”

Self-Supported N-Heterocyclic Carbenes and Their Use as Organocatalysts

“…Our group has had a longstanding interest in studying polymer-supported catalysts and reagents in general [31,32,33,34], and we have recently reported a self-supported oxime ligand for use in Pd-catalyzed Suzuki-Miyaura reactions [35]. This research has motivated us to examine self-supported imidazolium and benzimidazolium salts with flexible linker groups as NHC organocatalyt precursors.…”