CHEMICAL ENGINEERING TRANSACTIONS VOL. 83, 2021 A publication of The Italian Association of Chemical Engineering Online at www.cetjournal.it Guest Editors: Jeng Shiun Lim, Nor Alafiza Yunus, Jiří Jaromír Klemeš Copyright © 2021, AIDIC Servizi S.r.l. ISBN 978-88-95608-81-5; ISSN 2283-9216 NaOH-Promoted Reduction of Carbonyl Compounds Assisted by Microwave Uyen Phuoc Nhat Tran Van Hien University, 613 Au Co St, Phu Trung Ward, Tan Phu Dist, Ho Chi Minh City, Viet Nam. uyentpn@vhu.edu.vn The reduction of aldehydes and ketones based on MPV chemistry is one of the vital transformations in organic chemistry. In this study, MPV chemistry was developed in heating assistance of Microwave to synthesize a broad range of alcohol with yields up to 96 % by a simple, cheap, and safe synthetic protocol. Sodium hydroxide (NaOH) is an excellent promoter for the reduction. The method is quite cheap and straightforward while it utilized easy-to-handle chemicals and did not require strictly anhydrous reagents, transition metals, or any additional ligands. This potential method encourages a scale-up upgrading of Microwave use for alcohol production. 1. Introduction The development of sustainable synthetic methods directed recently is due to the heightened awareness of humans and the recognition of eco-friendly and economic methodologies that minimize negative impacts on the environment (Rathi et al., 2015). Among those, microwave-assisted methods have matured and have been used safely to substitute for conventional heating techniques (Prieto et al., 2019). Microwave was applied successfully in many fields such as bioenergy recovery (Ani et al., 2020), encapsulation (Muhamad et al., 2020), phytochemical extraction (Abd Rahman et al., 2020). Also, many microwave-heated chemical transformations have been achieved (Ni et al., 2020), thereby upgrading existing protocols to form superior results compared to normal heated ones (Zhou et al., 2020). Esterification, oligolactic acid synthesis, aromatic polyester synthesis are synthetic types whose methods were developed to have scale-up applications of microwave (Nagahata and Takeuchi, 2019). The reduction of aldehydes and ketones is one of the essential functional group transformations in organic chemistry. Meerwein Ponndorf Verley (MPV) reduction is recognized as one of such efficient transformations due to many desirable features such as high selectivity, mild conditions, and relatively cheap reagents (Cha, 2006). MPV reactions are normally catalyzed homogeneously by metal alkoxides such as aluminum isopropoxide Al(OiPr)3 (Cha, 2006). The reaction proceeds a hydride transfer from alcohol to carbonyl compound, which is coordinated to the metal center of alkoxide. The catalytic activity of these alkoxides is related to their Lewis acidic character in combination with ligand exchangeability (Cohen et al., 2004). In recent years, modifications of MPV reactions have been introduced to address some of the remaining problems, including long reaction times, solvent selection, side reactions, workup issues, and catalyst effectiveness by exploring novel catalytic systems. However, the cost and toxicity of transition metals (Bruneau-Voisine et al., 2017) and the sophisticated preparation of ligands (Zheng et al., 2020) needed to enhance MPV reduction are attributed to be typical drawbacks of this reaction. Boron alkoxides B(OR)3, an environmentally friendly candidate, could catalyze MPV reductions as metal alkoxides but it remained long reaction time, high content of alkoxides and limited subtract scope (Uysal and Oksal, 2011). To expand upon this trend in a different approach to build up a metal-free protocol, sodium tetraborate (Na2B4O7) was chosen as a catalyst for the MPV reaction in initial tests of this study. However, the unnecessary presence of Na2B4O7 in those tests led us to explore another metal-free alternative. Highly positive thermal effects of Microwave (conduction and dipolar polarization mechanism) encouraged us to use it to replace traditional heat transfer. To achieve a more sustainable alcohol synthesis that overcomes the weakness of alkoxide or metal catalytic system, an alkoxide-free and metal-free MPV method in the effective combination of the low base concentration and the crucial microwave heating was developed. The base- DOI: 10.3303/CET2183021 Paper Received: 25/06/2020; Revised: 06/08/2020; Accepted: 06/08/2020 Please cite this article as: Tran U.P.N., 2021, NaOH-Promoted Reduction of Carbonyl Compounds Assisted by Microwave, Chemical Engineering Transactions, 83, 121-126 DOI:10.3303/CET2183021 121