Selective Mixed Tishchenko Reaction via Substituted 1,3-Dioxan-4-ols

Abstract

Monoesters of 1,3-diols can be prepared with the mixed Tishchenko reaction from -hydroxy aldehydes and another aldehyde. These two aldehydes form a diastereomeric mixture of 1,3-dioxan-4-ol hemiacetal derivatives which can be further converted to monoesters with suitable catalysts. Limitations in the formation and esterification of this hemiacetal intermediate have been investigated in this work and the formation and stability of 1,3-dioxan-4-ols was found to be aldehyde-, temperature-, and solvent-dependent. A new method was developed for selective preparation of monoesters of 1,3-diols with this mixed Tishchenko reaction via 1,3-dioxan-4-ols without any significant side products. During the development of this method a possibility to scale up the reactions to reach a selective and economical process was one of the main targets in this work.

Thionium Ion Initiated Medium-Sized Ring Formation: The Total Synthesis of Asteriscunolide D

“…Aldol addition of isobutyraldehyde to formaldehyde conveniently provided the β-hydroxy aldehyde by precipitation of the dimer 15 , which could be triturated and used without further purification. 15 As depicted in Scheme 1, cracking of the dimer (60 °C, CH 3 CN) and subsequent HWE-olefination using the Masamune-Roush conditions (dimethyl 2-oxobutanephosphonate) 16 provided enone 16 , which was oxidized (Moffatt–Swern) to afford the aldehyde 10 . Gratifyingly, 10 served as an excellent substrate in the chemoselective Zn-ProPhenol catalyzed enantioselective addition with methyl propiolate to provide the γ-hydroxy propiolate 9 in good yield and enantiopurity.…”

Insights into Deactivation and Regeneration of an Industrial Cu/Ni/Cr‐Al2O3 Catalyst During Aldehyde Hydrogenation

“…Aldol condensation occurs only slightly resulting in 2.7 w % of the corresponding C 18 ‐condensate. For the thermal degradation, the aldol adduct undergoes a aldol‐Tishchenko reaction (see Figure ), which leads to higher hydrocarbon species and results in 40.4 w % of highboilers . In contrast, the reaction of nonyl aldehyde at 180 °C in the presence of the catalyst support (Table ), yields mainly the dimer (in this case in its unhydrogenated form; M =266 g mol −1 ).…”

Efficient Biocatalytic Synthesis of (R)‐Pantolactone

“…Heating at 65 8C in THF [14] or without solvent at elevated temperatures (! 100 8C) [15] are common procedures to shift the equilibrium to the monomer. As reported previously, [16] we observed unwanted byproduct formation via an anomalous Tishchenko reaction when the aldehyde was stirred at elevated temperatures.…”