Platinum-Catalyzed Ring Opening of 1,2-Cyclopropanated Sugars withO-Nucleophiles. Convenient Synthesis of 2-C-Branched Carbohydrates

Abstract

A new reaction is described catalyzed by Zeise's dimer that allows for ring opening of 1,2-cyclopropanated sugars with O-nucleophiles to give 2-C-branched carbohydrates. A number of Onucleophiles can participate in the ring opening including alcohols, phenols, and water. A wide range of alcohols has been employed giving 2-C-branched glycosides ranging from simple methyl glycosides to more complex disaccharides. A very high diastereoselectivity is obtained at the newly formed C-1 stereocenter. The R-glycoside, favored by the anomeric effect, is always the major product in the ring opening with alcohols regardless of the stereochemistry of the starting cyclopropane. When electron-rich phenols are employed as O-nucleophiles, rearrangement to the glycosyl arene has been observed. In general, the ring opening occurs readily with unsubstituted sugar cyclopropanes to give 2-C-methyl carbohydrates. However, cyclopropanes with ester or alkyl substituents are significantly less reactive and some even completely inert to ring opening. When the ring opening is carried out with PdCl 2 (PhCN) 2 catalyst, a Ferrier-type rearrangement occurs, giving 2,3-unsaturated glycosides containing a 2-C-alkyl substituent.

A Combined Gas‐Phase Photoelectron Spectroscopic and Theoretical Study of Zeise’s Anion and Its Bromine and Iodine Analogues

“…Besides being a historically key species in the field of organometallic chemistry in defining new chemical concepts (such as hapticity) and modes of chemical bonding, Zeise’s salt and its dimer have also been found to be effective in many important catalytic processes,21–23 as well as being used as versatile chiral derivatizing agents in asymmetric synthesis 24. 25 The Br analogue of Zeise’s salt is an important intermediate and was shown to activate the hydroamination of ethylene 26.…”

A Combined Gas‐Phase Photoelectron Spectroscopic and Theoretical Study of Zeise’s Anion and Its Bromine and Iodine Analogues

“…[7][8][9] These findings can be qualitatively explained by the DCD bonding model, [3,4] and have been essentially confirmed by earlier molecular orbital calculations [13,14] and related theoretical studies. [15][16][17][18][19][20] Besides being a historically key species in the field of organometallic chemistry in defining new chemical concepts (such as hapticity) and modes of chemical bonding, Zeises salt and its dimer have also been found to be effective in many important catalytic processes, [21][22][23] as well as being used as versatile chiral derivatizing agents in asymmetric synthesis. [24,25] The Br analogue of Zeises salt is an important intermediate and was shown to activate the hydroamination of ethylene.…”

Platinum‐Catalysed Ring‐Opening Isomerisation of Piperidine Cyclopropanes

“…A mechanism may be proposed by adapting that put forward by Madsen (Scheme ) . Regioselective oxidative addition of platinum(II) to the cyclopropane 2 gives a platinacyclobutane 5 which undergoes ring opening to give a η 1 ‐complex 6 a containing an iminium ion.…”