Solution-phase organic synthesis on soluble tags has developed as an alternative to the heterogeneous resin-supported and combinatorial methodologies. Efforts to design the tags have led to investigation of the effects of high reactivity of the soluble species and the possibility of using routine analytical methods (NMR, TLC, MS,
etc.). In particular, hydrophobic tag strategies have been recognized as useful methods which result in effective generation of target products. Towards the separation of tagged products, liquid-liquid extractions (LLE) may also have broad potential, because suitably tagged compounds in a biphasic system often show particular affinity for one phase without further supports. A recent study opened the door to the use of thermomorphic systems which can be applied in the form of a recyclable catalytic system in palladium- catalyzed cross-coupling and other reactions. In this paper, our recent research on the construction of cycloalkane-based thermomorphic solution systems with the hydrophobically tagged compounds. Organic reactions in homogeneous organic solutions, the reaction mixture gave the phase-separation just by cooling or addition of organic solvents. Desired products were immediately separated as a cycloalkane solution that could be successively used for following multi-step reactions. The biphasic solution system has been applied for electrochemical reactions, multi-step peptide, oligo-saccharide, and glyco-peptide syntheses featuring multi-step rapid and efficient reaction/separation process.
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