Cobalt-Catalyzed Deprotection of Allyl Carboxylic Esters Induced by Hydrogen Atom Transfer

Abstract

A brief, efficient method has been developed for the removal of the allyl protecting group from allyl carboxylic esters using a Co­(II)/TBHP/(Me2SiH)2O catalytic system. This facile strategy displays excellent chemoselectivity, functional group tolerance, and high yields. This transformation probably occurs through the hydrogen atom transfer process, and a Co­(III)–six-membered cyclic intermediate is recommended.

Electrocatalytic Oxidative Hydrofunctionalization Reactions of Alkenes via Co(II/III/IV) Cycle

“…Under the electrocatalytic conditions, methanol was found to add across a vinyl ether ( 5 ) in Markovnikov-selective fashion (Figure a). Inspired by recent reports on HAT-initiated alkene isomerization under chemical oxidation or electroreduction conditions , as well as results from our own lab, we envisioned a tandem isomerization/hydromethoxylation reaction that leads to trapping at the more cation-stabilizing site (Figure b). The in situ hydrolysis of the resulting acetal would provide a cheap and chemoselective means for allyl deprotection, which is alternative to strong base-mediated or precious metal-catalyzed methods .…”

Palladium-Catalyzed Ligand-Free ortho-Deuteration of Aromatic Carboxylic Acids with D2O

“…Subsequently, substrates with a different scaffold were tested. The deuteration of 1-naphthoic acid (27) showed the exchange occurred by both the six-and five-membered metallocyclic intermediates. A lower result for the 1-position of 2-naphthoic acid ( 28) could be accounted for by a higher steric hindrance.…”

Palladium Mediated Selective Cleavage of Benzyl and Allyl Phosphates: A Convenient Non‐Hydrogenolytic Method for the Synthesis of Phosphates and Phospholipids.

“…Synthesis of phospholipids and glycolipids involve extensive use of orthogonal protection -deprotection methods. [1][2][3] For instance much effort has been invested in the synthesis of inositol derived phosphates and phospholipids in the recent past. [4][5][6][7] These efforts showcase the extent of investment, in terms of effort and time, required in the development of orthogonal protection -deprotection strategies during the synthesis of phospholipids carrying various head groups.…”

“…Since these allyl group removal conditions could involve the use of strong acidic and / or basic conditions, they might not be compatible with several functional groups, especially in polyol-derived lipids.Hence, discovery and development of novel conditions for the protection and deprotection of functional groups continues to be of contemporary interest and practitioners of organic synthesis feel the necessity of newer, selective and better methods of protection and deprotection, in tune with the continuous advances and demands in synthetic organic chemistry. [2,3] We had earlier shown that benzyl and allyl ethers can be cleaved to liberate the parent alcohols using palladium hydroxide (Pearlmann's catalyst) in alcoholic solvents under neutral conditions. [8,9] We herein show that benzyl and allyl phosphates can be selectively cleaved non-hydrogenolytically using palladium (II) hydroxide.…”

“…Organic phosphates constitute a class of biologically active compounds, which are frequent synthetic targets for chemists. Synthesis of phospholipids and glycolipids involve extensive use of orthogonal protection – deprotection methods [1–3] . For instance much effort has been invested in the synthesis of inositol derived phosphates and phospholipids in the recent past [4–7] .…”