Mechanistic considerations and characterization of ammonia-based catalytic active intermediates of the green Knoevenagel reaction of various benzaldehydes

Abstract

(2019) Mechanistic considerations and characterization of ammonia-based catalytic active intermediates of the green Knoevenagel reaction of various benzaldehydes,

A Journey from Thermally Tunable Synthesis to Spectroscopy of Phenylmethanimine in Gas Phase and Solution

“…Here, we propose a putative hydrolytic pathway (Scheme 1) which is compatible with the aforementioned observations and with previously proposed mechanisms [46–48] . As noted above, the additional pathway leading to the formation of BN starting from PMI during the microwave spectroscopic measurements is supposed to be a dehydrogenation.…”

“…Here, we propose ap utative hydrolytic pathway (Scheme1) which is compatible with the aforementioned observations and with previously proposed mechanisms. [46][47][48] As noted above,t he additional pathway leading to the formation of BN startingf rom PMI during the microwaves pectroscopic measurements is supposed to be ad ehydrogenation.I no ur opinion, the following key pointsn eed to be analyzed to explain the proposedm echanism:( i) the role of water;( ii)the role of the metallic surface in the COBRA-FTMW spectrometer with respect to the glass surfaces acting in the FM-mmW experiment. Within the former context, water is expected to play ac rucial role:t he hydrolytic pathway is supposed to proceed as long as water is available.…”

The Knoevenagel reaction: a review of the unfinished treasure map to forming carbon–carbon bonds

“…In the Doebner and the Verley modifications, the use of pyridine is still a necessity as it plays a significant role as both solvent and catalyst in the reaction. Subsequently, the Verley modification also shows that pyridine not only acts as a base in the condensation step but undoubtedly promotes the decarboxylation reaction (39,40). The addition of β-alanine is regarded as a decent "green" substitution for piperidine (41).…”

Repeatable molecularly recyclable semi‐aromatic polyesters derived from lignin

“…Previously, a green, efficient, and scalable method has been developed, producing cinnamic acid analogs from 4‐hydroxybenzaldehydes 1 by condensation with malonic acid. [ 19,20 ] The calculated E‐factors in the low range of 1–2 are remarkable for a transformation that produces fine chemicals that typically have E‐factors in the range of 5–100. [ 21 ] Because the environmental impact of ammonium bicarbonate is relatively low, the unfriendliness quotient Q is probably also small but needs further investigation.…”