Robust Organocatalysts for the Cleavage of Vegetable Oil Derivatives to Aldehydes through Retrobenzoin Condensation

Abstract

A series of thiazolium salts was prepared and tested for the cleavage of the α-hydroxyketone derived from methyl oleate. The robustness of these precatalysts was determined by dynamic thermogravimetric analyses (TGA). It has been shown that the stability of these species is mainly governed by the nature of the counter-anion and some of them were found to be stable until 350-400 °C. The α-hydroxyketone derived from methyl oleate was cleaved under reactive distillation conditions using optimized, thermally robust N-butylthiazolium triflate to give the cleavage product, namely, nonanal and methyl azelaaldehydate, with 85 and 70 % yields. A range of α-hydroxyketones derived from several fatty acids was cleaved to give the corresponding bio-based aldehydes with up to 98 % isolated yields. Finally, this protocol was successfully applied to a high-oleic sunflower oil derivative.

Enzymatic Synthesis of Aliphatic Acyloins Catalyzed by Thermostable Transketolase

“…Screening of TK gst . Selected variants were screened by a colorimetric pH-based assay using phenol red as pH indicator [17] . In a 96well plate, 50 μL of HPA or 1 b or 1 c (100 mM) were mixed with 160 μL of aliphatic aldehyde (50 mM), 10 μL of TK (4 mg. mL À 1 ), 10 μL of MgCl 2 (25 mM) and 10μL of ThDP (2.5 mM).…”

“…[14] Our previous results with TK gst demonstrated excellent evolvability, [10][11][12][13] robustness against elevated temperatures and high tolerance to organic cosolvents. [15,16] These advantages render this biocatalyst particularly suitable for the synthesis of aliphatic acyloins, which are of particular interest in a research program focused on the green valorization of vegetable oil derivatives (i. e. fatty α-hydroxyketones) [17] where they will be used as model structures.…”

Aerobic Oxidative Cleavage of Vicinal Diol Fatty Esters by a Supported Ruthenium Hydroxide Catalyst

“…4 Novamont has proposed a two-step alternative process in which the cleavage of the diol is performed with homogeneous cobalt catalyst in water using air as oxidant. 15 Lab-scale processes have been proposed but the presence of an excess of base 17 , chlorinated by-products 18 or multi-steps processes 29,31 (Table 3) limits their practical use. Our process deals with the replacement of a homogenous catalytic system 15 by heterogeneous catalysis without an added base.…”

“…Proposed aerobic oxidation pathway of products with one carbon less than expected (i.e. compounds 13 from aldehyde 7) (adapted from25,[27][28] A mixture of aldehydes 7 and 8 (60/40) was synthesized according to the work of Lemaire et al29 and was oxidized under similar experimental conditions. At 150°C, the total conversion of a mixture of aldehydes 7 and 829 was obtained in less than 30 min(Figure 7).…”

Organocatalytic Cleavage of Fatty 1,2-Diketones to Esters

“…39 Alternatively, they can be cleaved to aldehydes through a retro-benzoin process catalyzed by thiazolium salts under reactive distillation conditions. [40][41][42] However, to the best of our knowledge, no example has been reported for the cleavage of fatty 1,2-diketones to the corresponding acids or esters. Actually, there are very few examples for the cleavage of 1,2-diketones (-diketones).…”