Hiromi Hamamoto

Novel Recycling System for Organic Synthesis via Designer Polymer-Gel Catalysts

In modern synthetic organic chemistry, the development of efficient reagent or catalyst recycling systems is regarded as one of the most important topics.1-6 The use of polymer supports is one of the potential approaches for this purpose, and the immobilization of reagents or catalysts on polymer supports offers a number of important advantages over their traditional homogeneous counterparts.7-29 For example, their separation from reaction products is easy and their potentiality for the consecutive recycling steps is accessible for a green chemical process. In addition, the immobilization on polymeric supports often causes the stabilization of sensitive catalyst and provides the potential applicability to intelligent materials. Despite these advantages, solid-phase catalyst is commonly difficult to retain or raise the activities relative to their homogeneous counterparts. Because of this significant disadvantage, solid-phase reaction system diminishes its synthetic utility in many cases. In recent years, much attention has been focused on the creation of reagent or catalyst recycling that exploits multifunctionalized materials via thermomorphic effect (Scheme 1). The use of a biphasic reaction system employing ionic liquids or fluorous solvents to hold efficient catalytic activity is recognized as a potential strategy.30-74 The main concept of these methods is to utilize the thermomorphic phase behavior and distribution of catalysts in the solvent for efficient recycling without loss of catalytic activity. The popularity of these systems has significantly increased over the past decade.

Enhancement of stereoselectivities in asymmetric synthesis using fluorinated solvents, auxiliaries, and catalysts

Organofluorine compounds find diverse applications in the medicinal, agricultural, and material sciences. As a new application, certain organofluorine compounds have been used as ancillary materials in asymmetric synthesis. In this paper, we introduce the asymmetric transformations in which fluorinated solvents, additives, auxiliaries, and catalysts function to improve the stereoselectivities and/or the chemical yields.

A synthesis of all stereoisomers of tenuecyclamide A employing a fluorous-Fmoc strategy.

A concise liquid-phase combinatorial synthesis of all stereoisomers of Tenuecyclamide A was achieved using a mixture of D-/L-alanine with each stereoisomer encoded by a different f-Fmoc tag. The synthetic strategy using f-Fmoc reagents as the protecting group for amino acids has been demonstrated to be a useful method for diverse polypeptide analogue synthesis.

DECARBOXYLATIVE BROMINATION OF INDOLE-2,3-DICARBOXYLIC ACIDS USING OXONE® OR CAN IN THE PRESENCE OF LITHIUM BROMIDE

The treatment of 1-methylindole-2,3-dicarboxylic acid with Oxone® and lithium bromide produced 3,3-dibromo-1-methyloxindole. However, the reaction of 1-benzenesulfonylindole-2,3-dicarboxylic acid with Oxone® and lithium bromide afforded 1-benzenesulfonyl-2,3-dibromoindole. In a similar manner, 2,3,5,6-tetrabromoindole was synthesized from 1-benzenesulfonyl-5,6- dibromoindole-2,3-dicarboxylic acid.

Nitration of dimethyl 1-substituted indole-2,3-dicarboxylates: synthesis of nitro- and aminoindole derivatives

The treatment of dimethyl indole-2,3-dicarboxylate with nitronium tetrafluoroborate in the presence of tin (IV) chloride produced dimethyl 5-nitroindole-2,3-dicarboxylate as the major product. In a similar manner, the dimethyl 1-benzyl- and 1-benzenesulfonylindole-2,3-dicarboxylates provided a mixture of the corresponding 4-nitro-, 5-nitro-, 6-nitro- and 7-nitroindole derivatives. However, dimethyl 5-bromoindole-2,3- dicarboxylate gave dimethyl 5-bromo-4-nitroindole-2,3-dicarboxylate as the sole product, which was converted to dimethyl 4-aminoindole-2,3-dicarboxylate.