Acrolein dimerization

Acrolein is produced according to the specifications in Table 3. Acetaldehyde and acetone are the principal carbonyl impurities in freshly distilled acrolein. Acrolein dimer accumulates at 0.50% in 30 days at 25°C. Analysis by two gas chromatographic methods with thermal conductivity detectors can determine all significant impurities in acrolein. The analysis with Porapak Q, 175—300 p.m (50—80 mesh), programmed from 60 to 250°C at 10°C/min, does not separate acetone, propionaldehyde, and propylene oxide from acrolein. These separations are made with 20% Tergitol E-35 on 250—350 p.m (45—60 mesh) Chromosorb W, kept at 40°C until acrolein elutes and then programmed rapidly to 190°C to elute the remaining components. 

Production of Acrolein Dimer. Acting as both the diene and dienoplule, acrolein undergoes a Diels-Alder reaction with itself to produce acrolein dimer, 3,4-dihydro-2-formyl-2id-pyran, CgHg02 [100-73-2], At room temperature the rate of dimerization is very slow. However, at elevated temperatures and pressures the dimer may be produced in single-pass yields of 33% with selectivities greater than 95%. 

Acrolein dimer may be easily hydrated to a-hydroxyadipaldehyde, [141-31-1] which may then be reduced to 1,2,6-hexanetriol [106-69-4]. 

In connection with studies on the ring-opening polymerization of cyclic acetals, we have undertaken investigations on the polymerization of bicyclic acetals, bicyclic oxalactone, and bicyclic oxalactam, which yield polysaccharide analogs, macrocyclic oligoesters, and a hydrophilic polyamide, respectively, some of which can be expected to be useful as novel speciality polymers. The monomers employed in the studies were prepared via synthetic routes presented in Scheme 1, starting from 3,4-dihydro-2H-pyran-2-carbaldehyde (acrolein dimer) I. 

Stereoselective addition to an a-alkoxy aldehyde.3 The addition of organo-metallic reagents to acrolein dimer 1 can be controlled to a remarkable extent by the metal, evidently as a result of chelation, with R2Zn being more stereoselective than RLi or RMgBr. 

In order to obtain levoglucosenone 1 in both enantiomeric forms by employing lipase-mediated kinetic resolution, we used acrolein dimer 2 as the starting material.4 2 was first transformed to the bicyclic ketone ( )-6 by sequential four steps of reactions via 3-5. Racemic levoglucosenone ( )-l was obtained from 6 via the silyl ether 7 by employing the Saegusa reaction. To carry out lipase-mediated resolution, ( )-l was transformed into the e/wfo-alcohol ( )-8 and the acetate ( )-9 (Scheme 1). 

For the synthesis of exo-brevicomin 617, the acrolein dimer was transformed mainly into the threo-DHP 614 by addition of ethylmagnesium bromide and chromatographic... 

Acrolein dimer may be easily hydrated to a-hydroxyadipaldehyde, C H1( iO, [141-31-1] which may dien lie reduced to 1,2,6-hexanetriol [106-69-4]. 1,2,6-Hexanetriol, C6H1403, is used in a variety of pharmaceutical and cosmetics industry applications and is currently viewed as an alternative to glycerol as a liumectant. 

SYNS ACROLEIN DIMER, stabiUzed (DOT) 3,4-DIHYDRO-2H-PYRAN-2-CARBOXALDEHYDE 2,3-DIHYDRO-L4-PYRAN-2-KARBOXALDEHYD 2-FORMYL-3,4-DIHYDRO-2H-PYRAN 5-HEXENAL, 2,6-EPOXY- a PYTIAN ALDEHYDE... 

Table 4 Addition of Organometallic Reagents to Acrolein Dimer (7)...

Pyranyl foams are prepared by the cationic polymerization of pyranyl monomers in the presence of a catalyst and a surfactant. The pyranyl monomers are prepared via acrolein and acrolein dimer. 

Pyranyl Monomer. Pyranyl monomers are prepared according to the following reactions (1-7). Acrolein is converted to acrolein dimer, e.g., by means of a Shell patent (8), which then leads to pyranyl monomers by different reactions including the Tischenko reaction and the Diels-Alder reaction. Some of the reactions are shown below. 

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