ceverelst

Immobilization: Heteropolyacids gained attention as catalysts for the valorization of lignocellulose. They show good solubility in water and various solvents, making their recycling rather difficult. We focus on recent publications investigating solidification or immobilization strategies of heteropolyacids as catalysts for biomass valorization. An emphasis is laid on surveying recycling strategies and elucidating structure-activity relationships.

Abstract

Heteropolyacids have been identified as promising for catalyzing the reaction types, hydration and dehydration, which play an important role in the valorization of lignocellulose. Not only do they possess adaptable Brønsted acidity, but they also show a redox multi functionality. To increase the industrial applicability of this promising class of catalysts and to enable recycling, many different approaches for immobilization (such as multiphasic catalysis or grafting) and solidification (such as salt formation) have been pursued in recent years. This review summarizes these efforts and highlights the studied acid-catalyzed lignocellulose conversions, trends and current challenges.

Synlett
DOI: 10.1055/s-0041-1737338

1,4,2-Dioxazol-5-ones are known to undergo decarboxylation under thermal conditions followed by Lossen’s rearrangement to give isocyanates. Described herein is the in situ trapping of the isocyanates by indoles to give indole-3-carboxamides in good to excellent yields.
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Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany

Article in Thieme eJournals:
Table of contents  |  Abstract  |  Full text

Smells like sustainability: Sustainable and high-yielding bioproduction of phenethyl acetate, phenylacetic acid, ethyl phenylacetate, and phenylethyl phenylacetate as high-value natural aroma chemicals are achieved from renewable feedstock l-phenylalanine with novel artificial enzyme cascades, or from glucose and glycerol with combined artificial enzyme cascades and natural pathway.

Abstract

Natural phenethyl acetate (PEA), phenylacetic acid (PAA), ethyl phenylacetate (Et-PA), and phenethyl phenylacetate (PE-PA) are highly desirable aroma chemicals, but with limited availability and high price. Here, green, sustainable, and efficient bioproduction of these chemicals as natural products from renewable feedstocks was developed. PEA and PAA were synthesized from l-phenylalanine (l-Phe) via novel six- and five-enzyme cascades, respectively. Whole-cell-based cascade biotransformation of 100 mm l-Phe in a two-phase system (aqueous/organic: 1 : 0.5 v/v) containing ethyl oleate or biodiesel as green solvent gave 13.6 g L⁻¹ PEA (83.1 % conv.) and 11.6 g L⁻¹ PAA (87.1 % conv.), respectively. Coupled fermentation and biotransformation approach produced 10.4 g L⁻¹ PEA and 9.2 g L⁻¹ PAA from glucose or glycerol, respectively. The biosynthesized PAA was converted to natural Et-PA and PE-PA by esterification using lipases with ethanol or 2-phenylethanol derived from sugar, affording 2.7 g L⁻¹ Et-PA (83.1 % conv.) and 4.6 g L⁻¹ PE-PA (96.3 % conv.), respectively.

Publication date: 20 January 2022

Source: Chem Catalysis, Volume 2, Issue 1

Author(s): Jie Gao, Lu Feng, Rui Ma, Bing-Jian Su, Asma M. Alenad, Yuefeng Liu, Matthias Beller, Rajenahally V. Jagadeesh