Formation of enantioenriched alkanol with stochastic distribution of enantiomers in the absolute asymmetric synthesis under heterogeneous solid–vapor phase conditions

Abstract

Among several theories proposed for the origin of homochirality, absolute asymmetric synthesis is unique because it produces chiral compounds without the intervention of any chiral factor. Here we report on the kinetically controlled heterogeneous solid-vapor phase absolute asymmetric synthesis in conjunction with asymmetric autocatalysis with amplification of chirality. Each reaction, carried out in a test tube, between achiral powder crystals of pyrimidine-5carbaldehyde and the vapor of diisopropylzinc, is controlled kinetically to afford either (S)-or (R)-pyrimidyl alkanol.Scheme 1 Absolute asymmetric synthesis initiated under (a) homogeneous and (b) heterogeneous conditions in conjunction with asymmetric autocatalysis with amplification of chirality.

Role of Asymmetric Autocatalysis in the Elucidation of Origins of Homochirality of Organic Compounds

“…As described, the results fulfill the conditions necessary for spontaneous absolute asymmetric synthesis [62,65,[114][115][116][117]. Very recently, absolute asymmetric synthesis under heterogeneous solid-vapor phase conditions has been reported by us (Scheme 10) [118]. The powder of pyrimidine-5-carbaldehyde 2c in test tubes was exposed to the vapor of i-Pr2Zn and toluene in a desiccator.…”

“…The present heterogeneous absolute asymmetric synthesis under solid vapor phase conditions could be possible in a more spacious platform. Very recently, absolute asymmetric synthesis under heterogeneous solid-vapor phase conditions has been reported by us (Scheme 10) [118]. The powder of pyrimidine-5-carbaldehyde 2c in test tubes was exposed to the vapor of i-Pr 2 Zn and toluene in a desiccator.…”

Absolute Autocatalytic Amplification Under Heterogenous Conditions Involving Subsequent Hydride Transfer and Hemiacetal Intermediate.

“…Just recently, this study was extended with an absolute asymmetric synthesis under kinetic control of vapor-solid phase of reaction of iPr2Zn with aldehyde 1. [16] Figure 1. Figure Caption. Initially, we examined the behavior of pyrimidine-5carboxaldehyde 1 in presence of pyridine-3-carboxaldehyde 3 in a 1:1 stoichiometry.…”

“…Thus, in presence of a same iPr2Zn atmosphere, amplification of alkanol 4 is not subject to a chiral trigger as shown previously. [16] Closer analysis of crude material indicates the presence of ketone 5 and reduction alcohol 6. Furthermore, and perhaps more interesting formation of chiral ester 7 and achiral 8 is also On the other side, the only possible mechanism of formation of esters 7 and 8 is through a Claisen-Tishchenko reaction following a Cannizaro disproportionation mechanism.…”

Absolute Autocatalytic Amplification Under Heterogenous Conditions Involving Subsequent Hydride Transfer and Hemiacetal Intermediate.

“…Just recently, this study was extended with an absolute asymmetric synthesis under kinetic control of vapor-solid phase of reaction of iPr2Zn with aldehyde 1. [16] Initially, we examined the behavior of pyrimidine-5carboxaldehyde 1 in presence of pyridine-3-carboxaldehyde 3 in a 1:1 stoichiometry. Five reactions with the setup of Fig.…”