Silver carbonate

Abstract

(A) Oxidation of Alcohols: Fetizons reagent (silver carbonate on celite) is known to be a mild oxidizing agent capable of converting alcohols into aldehydes and ketones. Here, this reagent is applied in the complex setting of an enantioselective total synthesis of (+)-upial.4 The desired lactone was obtained from the corresponding lactol in excellent 94% yield. (B) 5-Exo-dig Cyclization of Alcohols and Carboxylic Acids: Alcohols containing a proximal acetylenic part5 and isoindolones containing γ-acetylenic carboxylic acid moieties6 can be efficiently cyclized using a catalytic amount of Ag 2CO 3. (C) Halogen Scavenger; Generation of Nitrilimines: The azeto[3′,4′:2,3]pyrano[4,5-c]pyrazole skeleton holds potential interest as a b-lactamase-resistant antibiotic. An enantioselective route towards one member of this class was developed from the intramolecular [3+2] cycloaddition of a nitrilimine and a proximal alkene. The nitrilimine was generated via chlorine abstraction from the parent hydrazonoyl chloride using silver carbonate. (D) Halogen Scavenger; C-H Oxidation Strategy: In landmark work, a C-H oxidation strategy was employed for the synthesis of eudesmane terpenes. The syntheses of two of them, dihydroxyeudesmane and pygmol, feature as key steps the selective bromination of the more reactive tertiary carbon from the isopropyl sidechain, followed by a cyclization event assisted by silver carbonate. After hydrolysis of the cyclic carbonate formed, the corresponding diol is obtained in a very selective manner. (E) Halogen Scavenger: Aziridinium Ion Formation: A chiral anion phase-transfer catalysis was established by taking advantage from the low solubility of silver carbonate and the generally high solubility of (S)-TRIP salts in organic solvents. Silver carbonate abstracts the chlorine atom to generate an aziridium phosphate ion pair, whose chiral anion directs the enantioselective nucleophilic aziridinium ring opening to afford the corresponding amino ethers in good yields and excellent enantioselectivities. (F) Base/Oxidant for Decarboxylative Cross-Coupling: An efficient, regio- and chemoselective palladium-catalyzed intramolecular arylation of benzoic acid derivatives by means of a decarboxylation/C-H activation sequence using silver carbonate as base and oxidant of choice has been described. (G) Oxidant for Olefination-Michael Addition Sequence: The use of dinuclear rhodium species [Cp*RhCl 2] 2 as catalyst and Ag 2CO 3 as oxidant allows direct access to Heck cross-coupled products without the need for prior arene functionalization. The styrene product obtained undergoes spontaneous Michael addition under the reaction conditions to afford the corresponding cyclized products in good yields. © Georg Thieme Verlag Stuttgart · New York.