Dae Hyan Cho

Enantioselective radical addition reactions to the C=N bond utilizing chiral quaternary ammonium salts of hypophosphorous acid in aqueous media

An enantioselective addition of alkyl radicals to glyoxylate oxime ether mediated by Cinchona alkaloid derived chiral ammonium salts of hypophosphorous acid, QP and QDP, has been developed.

Radical deoxygenation of alcohols and vicinal diols with N-ethylpiperidine hypophosphite in water

Radical deoxygenation of alcohols and vicinal diols with N-ethylpiperidine hypophosphite both in alcohols and in water is described. S-Methyl dithiocarbonate and bis-S-methyl dithiocarbonate of carbohydrates and nucleosides were deoxygenated efficiently under reaction conditions.

Radical deoxygenation of alcohols via their trifluoroacetate derivatives with diphenylsilane

Abstract Trifluoroacetate derivatives of alcohols can be used as precursors for the radical deoxygenation of alcohols with diphenylsilane. The reaction afforded high isolated yields of the deoxygenated products and neutral reaction conditions.

Conversion of esters and lactones to ethers via thionoesters and thionolactones using reductive radical desulfurization

Abstract Various thionoesters and thionolactones are readily reduced into the corresponding ethers in high isolated yields by radical desulfurization with organotin hydrides and Et 3 B under mild reaction conditions.

One-Pot Preparation of Esters from Carboxylic Acids Using the PPh3-CCl3CN System

Abstract A convenient one-pot process for preparing various esters from carboxylic acids using the Ph3P-CCl3CN has been developed. Racemic α-tocopherol, clofibrate and flavoxate were prepared in high yields using this method.

Efficient Synthesis of Epoxides from Vicinal Diols Via Cyclic Sulfates

Abstract Reaction of cyclic sulfates of vic-diols with sodium hydroxide in THF-MeOH produced the corresponding epoxides in excellent isolated yields at room temperature. Cyclic sulfates of trans-diols gave cis-epoxides, and cyclic sulfates of cis-diols afforded trans-epoxides exclusively. Various cyclic sulfates of vic-diols can be converted into the epoxides under the conditions.

A Method for Preparation of Unnatural (R)-Malic Acid Derivatives with Phenylsilanes

Abstract Enantiomerically pure unnatural (R)-malic acid derivatives were prepared from (R,R)-tartrates via their cyclic thionocarbonate derivatives using phenylsilanes in high isolated yields.

Synthesis of 2′,3′-Dideoxyinosine via Radical Deoxygenation

A synthetic method for 2 ′,3 ′-dideoxyinosine (ddI) from inosine was established via radical deoxygenation of N1,5 ′-O-diprotected-2 ′,3 ′-bis-S-methyl dithiocarbonate of inosine derivatives. The radical deoxygenation proceeded smoothly to give the desired dideoxy compounds in good yields using 1-ethylpiperidinium hypophosphite and triethylborane. Benzyl or p-methoxybenzyl protection of inosine at the N1, 5 ′-O-positions were effective for the ddI synthesis.

A Facile Route to Olefins from Vic-Diols Via Cyclic Sulfates with Triphenylphosphine and Iodine

Abstract Treatment of cyclic sulfates of vic-diois with triphenylphosphine and iodine offers the corresponding olefins in high yields at room temperature. Both cyclic sulfates of d,l-hydrobenzoin and meso-hydrobenzoin give trans-stilbene.

Carbon-Carbon Bond Formation by Cyclization of Dienes Using Phosphorus-Centered Radicals in Water

An efficient and mild methodology for preparing carbocyclic and heterocyclic compounds with phosphorus functionality by radical cyclization of dienes in water without using organic co-solvents has been developed. The reaction affords environmentally benign reaction conditions.