Study On Gluconic Acid Aqueous Solution As A Sustainable And Recyclable Promoting Medium For Organic Reactions

Many reactions, extractions, separations and other operations in the chemical processindustries involve the use of organic solvents. However, large scale uses of the organicsolvents are not only plagued by handling and disposal issues, but also can pose a numberof environmental concerns. In many cases, organic solvents are volatile and toxic, the useof these solvents will not only cause harmful effect to human health and the environment,but also plugued by the post treatment of organic waste liquid which is time-consuming andwaste of money. Therefore, seeking green solvents to replace traditional organic solventbecome one of research focus of green chemistry.This paper utilizes bio-based polyhydroxy acid, gluconic acid aqueous solution (50%), asreaction medium and catalyst for performing following reactions including (i) Michaeladdition of indole to,-unsatured carbonyl compounds;(ii) electrophilic ring-openingreaction of3,4-dihydropyran with indole; and (iii) Friedel-Crafts alkylations of indole withbenzyl alcohols. All these reactions can be performed smoothly in aqueous solution ofgluconic acid, providing the corresponding products in good to exellent yields. The use ofgluconic acid aqueous solution as reaction medium not only avoids the use of toxic, andsometimes, expensive catalysts, but also minimizes the generation of waste. In thesereactions, aqueous solution of gluconic acid could be easily recovered and reused at leastthree times without significant loss of its activity.In conclusion, aqueous solution of gluconic acid was demonstrated to be a promisinggreen solvent for performing organic reactions. The concept of using GAAS as solvent fororganic reactions not only offers a sustainable candidate for strengthening solventinnovation, but also opens a new avenue for utilization of this bio-based polyhydroxylatedacid.