Quantitative NMR Approach to Optimize the Formation of Chemical Building Blocks from Abundant Carbohydrates

Abstract

The future role of biomass-derived chemicals relies on the formation of diverse functional monomers in high yields from carbohydrates. Recently, it has become clear that a series of α-hydroxy acids, esters, and lactones can be formed from carbohydrates in alcohol and water solvents using tin-containing catalysts such as Sn-Beta. These compounds are potential building blocks for polyesters bearing additional olefin and alcohol functionalities. An NMR approach was used to identify, quantify, and optimize the formation of these building blocks in the Sn-Beta-catalyzed transformation of abundant carbohydrates. Record yields of the target molecules can be achieved by obstructing competing reactions through solvent selection.

Effects of Alkali‐Metal Ions and Counter Ions in Sn‐Beta‐Catalyzed Carbohydrate Conversion

“…To this end, the initial reaction rates were determined for varying concentrations of K 2 CO 3 . These rates are consistent with previously reported trends in product distributions for increasing concentrations of K 2 CO 3 . Rates of formation for dehydration products decline upon addition of K 2 CO 3 , in parallel with a drop in yield of these products upon addition of K 2 CO 3 .…”

“…The current study sets out to systematically study the effect of alkali‐metal salts (as demonstrated herein for potassium salts) on the divergent pathways catalyzed by Sn‐Beta (Scheme ). Quantitative high‐field NMR spectroscopy was used to distinguish and quantify various reaction products without the need for purification, reference compounds, or instrument calibration . Changes in activity and selectivity of Sn‐Beta were thus noninvasively probed by accurate in situ analysis of the resultant reaction mixtures.…”

NMR Spectroscopic Isotope Tracking Reveals Cascade Steps in Carbohydrate Conversion by Tin‐Beta

“…[1] Pentoses were selected because of their inherently asymmetric aldol cleavager eactions that enablet he further distinctiono fp roduct origins. [1] Pentoses were selected because of their inherently asymmetric aldol cleavager eactions that enablet he further distinctiono fp roduct origins.…”

“…[1] The deuterated carbon positions were identified from characteristic chemical shift changes to lower frequency andf rom characteristicm ultiplet patterns caused by coupling to quadrupolar 2 Hn uclei (Figure 3A). The resultanti sotopologueso fl actatew ere characterized by using NMR spectroscopy at am agnetic field of 18.7 T( 800 MHz instrumente quipped with cryogenically cooled detection electronics)u sing aq uantitative 13 CNMR (qNMR) spectroscopy approach demonstrated previously.…”

“…[1] In addition, the use of NMR spectroscopy may provide additional mechanistic insight into reaction cascades throught he characterization of isotope distributions in the products. Despite this interest, many routes of carbohydrate conversion to useful chemicals are complex and lack fundamentalp athway understanding.…”