Practical Method for Preparation of ()-2-Amino-5,5,5-trifluoropentanoic Acid via Dynamic Kinetic Resolution.

This work reports an operationally convenient ∼20 g scale synthesis of ()-2-amino-5,5,5-trifluoropentanoic acid and its Fmoc-derivative via dynamic kinetic resolution of the corresponding racemate.

Preparation of THP-ester-derived pyridinium-type salts and their reactions with various nucleophiles.

Nucleophilic substitution at the anomeric positions of tetrahydropyranyl (THP) and related carbohydrate-derived esters that proceeded through pyridinium-type salt intermediates have been developed. Treatment of the 6-substituted α-acetoxy-tetrahydropyrans with TMSOTf (TMS=trimethylsilyl) and 2-substitutited pyridines, such as 2-p-tolylpyridine and 2-methoxypyridine, led to the efficient generation of cis-pyridinium-type salts. These salts reacted with various nucleophiles, such as alcohols, azides, and organozinc reagents, to form nucleophilic-substitution products.

Mild deprotection of methylene acetals in combination with trimethylsilyl triflate-2,2'-bipyridyl.

The facile deprotection of methylene acetal protection of diols under mild conditions is established. The combination of trimethylsilyl triflate (TMSOTf) and 2,2'-bipyridyl followed by a weakly acidic hydrolysis was effective and the substrates having acid sensitive functional groups can be tolerated under the stated conditions. The selective deprotection between methylene acetal and benzophenone ketal was achieved.

Novel regiocontrolled protection of 1,2- and 1,3-diols via mild cleavage of methylene acetals.

The regiocontrolled protection of unsymmetrical 1,2- and 1,3-diols has been developed. Different types of protected diols are available from the methylene acetal in a one-pot procedure. Highly regioselective protection of diols with a silyl group at the less hindered hydroxy group as well as with a MOM group at the more hindered one were achieved.

Remarkable effect of 2,2'-bipyridyl: mild and highly chemoselective deprotection of methoxymethyl (MOM) ethers in combination with TMSOTf (TESOTf)-2,2'-bipyridyl.

The remarkable effect of 2,2'-bipyridyl led to the successful development of the mild and highly chemoselective deprotection method of methoxymethyl (MOM) ethers using the combination of TMSOTf (or TESOTf) and 2,2'-bipyridyl; this method can be applied to the direct conversion of the MOM group to other ethereal protective groups (e.g. benzyloxymethyl) with the corresponding alcohols.

A new H2O2/acid anhydride system for the iodoarene-catalyzed C-C bond-forming reactions of phenols.

We have succeeded in the first versatile iodoarene-catalyzed C-C bond-forming reactions by development of a new reoxidation system at low temperatures using stoichiometric bis(trifluoroacetyl) peroxide A in 2,2,2-trifluoroethanol (TFE). The catalytic system supplies a wide range of substrates and functional availabilities sufficient to be used in the key synthetic process of producing biologically important Amaryllidaceae alkaloids.

Versatile direct dehydrative approach for diaryliodonium(III) salts in fluoroalcohol media.

We have found that the use of fluoroalcohol media greatly enhanced the efficiency and scope of the direct dehydrative condensation of arenes and hypervalent iodine(III) compounds; the present clean method has a broad range of applicability as well as unique selectivity in the aromatic substrates, and is highly efficient even in polymer functionalization.

First hypervalent iodine(III)-catalyzed C-N bond forming reaction: catalytic spirocyclization of amides to N-fused spirolactams.

A protic solvent, 2,2,2-trifluoroethanol (CF(3)CH(2)OH), was successfully introduced into hypervalent iodine(III)-involved catalytic cycles as an effective solvent, and the first iodoarene-catalyzed intramolecular carbon-nitrogen bond forming reaction was achieved under strong acid-free and mild conditions.