No abstract

N-Butylpyrrolidinone (NBP) has been demonstrated as a suitable safer replacement solvent for N-Methylpyrrolidinone (NMP) in selected organic syntheses.

Short amines, such as ethanolamines and ethylenediamines, are important compounds in today's bulk and fine chemicals industry. Unfortunately, current industrial manufacture of these chemicals relies on fossil resources and requires rigorous safety measures when handling explosive or toxic intermediates. Inspired by the elegant working mechanism of aldolase enzymes, a novel heterogeneously catalyzed process-reductive aminolysis-was developed for the efficient production of short amines from carbohydrates at low temperature. High-value bio-based amines containing a bio-derived C2 carbon backbone were synthesized in one step with yields up to 87 C%, in the absence of a solvent and at a temperature below 405 K. A wide variety of available primary and secondary alkyl- and alkanolamines can be reacted with the carbohydrate to form the corresponding C2-diamine. The presented reductive aminolysis is therefore a promising strategy for sustainable synthesis of short, acyclic, bio-based amines.

Reductive amination of glycolaldehyde (GA), the smallest sugar molecule and obtainable from biomass, creates a versatile platform for ethylamine products, potentially replacing current pathways via toxic ethylene oxide and dichloroethane. Given the high reactivity of α-OH carbonyls, the main challenge was control of selectivity in a cascade of parallel and consecutive reactions during reductive amination. The type of solvent and catalyst, preferably methanol and Pd, respectively, are key enabling parameters to achieve high product yields. A kinetic study on product intermediates accompanied with detailed product analysis (MS and NMR) suggested a general mechanistic scheme and validation with density functional theory calculations provided a rational understanding of the solvent effect in terms of energetics and kinetics. Primary alkanolamines (AA) such as 2-(dimethylamino)-ethanol are preferred products, and large excess of the amine reagent is not required to reach almost quantitative yields. Interestingly substoichiometric amine-to-GA ratio allows for high yield of higher (consecutive) AAs such as N-methyldiethanolamine (MDEA) and triethanolamine, for which a peculiar cyclic 5-membered oxazolidinic precursor was analyzed (e.g., for reaction with monomethylamine to MDEA). The shift to diamine-selective (DA) reactions is possible by switching to a two-step one-pot approach. With ethylene glycol as a preferred solvent, high yield of an unsaturated C 2 -enediamine precursor is obtained under an inert atmosphere, followed by its metal-catalyzed hydrogenation at elevated temperature to the final DA product such as N,N,N′,N′-tetramethylethylene-diamine. A conceptual model of the catalytic reductive amination routes that allows production of a variety of ethylamines with up to +90 C % yield is thus presented. The successful preparation and sensory assessment of a GA-based diester quat in fabric softener formulations demonstrates the viability of a full bio-based and drop-in production route for high-value chemicals, directly from GA as a platform molecule.

Evidently so: New mechanistic findings indicate that addition of dialkyl trimethylsilyl phosphites to α,β‐unsaturated imines has been incorrectly reported as an exclusive 1,2‐addition. When α,β‐unsaturated imines are used as substrates, 1‐alkylamino 3‐phosphonyl phosphonates are formed in high yields in the presence of a suitable proton source through a sequential 1,4‐ and 1,2‐addition.

Fossil‐based platform molecules such as ethylene and ethylene oxide currently serve as the primary feedstock for the C2‐based chemical industry. However, in the search for a more sustainable chemical industry, fossil‐based resources may preferentially be replaced by renewable alternatives, provided there is realistic economic feasibility. This Review compares and critically discusses several production routes toward bio‐based structural analogues of ethylene oxide and the required adaptations for their implementation in state‐of‐the‐art C2‐based chemical processes. For example, glycolaldehyde, a structural analogue obtainable from carbohydrates by atom‐economic retro‐aldol reactions, may replace ethylene oxide's leading role. This alternative chemical route may not only allow the carbon footprint of conventional chemicals production to be lowered, but the introduction of a bio‐based pathway may also contribute to safer production processes. Where possible, challenges, drawbacks, and prospects are highlighted.

A new tandem reaction sequence has been developed for the synthesis of 2‐phosphono pyrroles. The sequence consists of ring‐closing enyne metathesis of a substituted aminophosphonate, containing a terminal alkyne and an internal alkene, in combination with in situ oxidation of the produced 3‐pyrrolines using tetrachloroquinone. By analyzing the formation of the end and certain byproducts, taking into account the difference in reactivity of different substrates and carefully studying spectroscopic data, it was found that the reaction proceeds by means of the “yne‐then‐ene” pathway. During the initiation phase, a new ruthenium carbene is formed which continues the propagation cycle.

Best aminated feature: Catalytic transformation of alcohols to amines is a fundamental transformation in synthetic organic chemistry. A general salt‐free Ir‐catalyzed amination of aliphatic alcohols and diols has been developed, which gives amino alcohols with high selectivity. By use of an Ir–pincer chlorodihydride complex, usually applied for the transfer hydrogenation of ketones, simple monoalcohols are aminated with excellent yields.