Enantioselective CC Bond Formation as a Result of the Oriented Prochirality of an Achiral Aldehyde at the Single‐Crystal Face upon Treatment with a Dialkyl Zinc Vapor

Abstract

Zeig deine beste Seite: Bei einem achiralen Pyrimidin‐5‐carbaldehyd, der einen achiralen Kristall (${{{\rm P}\bar 1}}$) mit enantiotopen (001)‐ und (${{00\bar 1}}$)‐Seiten bildet, addiert sich iPr2Zn enantioselektiv an die einzelne exponierte enantiotope Oberfläche unter Bildung hoch enantiomerenangereicherter sekundärer S‐ und R‐Alkohole (siehe Schema). Die Absolutkonfiguration des Alkoholprodukts korreliert mit der Ausrichtung des prochiralen Aldehyds im achiralen Kristallgitter.

Asymmetric Autocatalysis of Pyrimidyl Alkanol and Its Application to the Study on the Origin of Homochirality

“…In addition to the initial report of asymmetric amplification using asymmetric autocatalyst 3 without a substituent at the 2-position, 24 it was found that the 2-methyl-5-pyrimidyl alkanol 4 27 and the 5-pyrimidyl alkanols 5−12 possessing alkenyl 28 and alkynyl groups 25,29,30 at the 2-position, including 1, also exhibited a significant automultiplication functionality ( Figure 2). The 3-quinolyl alkanols 13−15 31 and 5-carbamoyl-3-pyridyl alkanol 16 32 are also highly efficient asymmetric autocatalysts.…”

“…We describe the enantioselective formation of C−C bonds to form 9 on the face of single crystal pyrimidine-5-carbaldehyde using i-Pr 2 Zn vapor (Scheme 6). 30 Scheme 7. Molecular Chirality Arising from Hydrogen, Carbon, and Oxygen Isotopes Substitution 2-tert-Butyldimethylsilylethynylpyrimidine-5-carbaldehyde crystallizes in an achiral form (P1̅ ), and when the crystal structure is projected perpendicular to the c-axis, either the Si or Re face of the formyl group is oriented toward the outside of the crystal.…”

“…Enantioface-selective oxidation and reduction with low-to-moderate ee at the enantiotopic surface has been reported. We describe the enantioselective formation of C–C bonds to form 9 on the face of single crystal pyrimidine-5-carbaldehyde using i -Pr 2 Zn vapor (Scheme ) …”

Asymmetric autocatalysis. Chiral symmetry breaking and the origins of homochirality of organic molecules

“…When one of these faces was exposed to the vapor of i -Pr 2 Zn, the exposed Re -face of aldehyde was attacked by i -Pr 2 Zn to afford ( R )-pyrimidyl alkanol 1f . 93) By contrast, exposure of the opposite enantiotopic face (the Si -face of aldehyde) afforded ( S )-alkanol 1f . The ee of the obtained alkanol was amplified to >99.5% by the subsequent asymmetric autocatalyses.…”

Observation of a Transient Intermediate in Soai’s Asymmetric Autocatalysis: Insights from 1H NMR Turnover in Real Time

“…Significant advances in the period since the initial discovery include absolute asymmetric synthesis, [5,6] amplification from extremely low to high levels of enantiomer excess, [7] and initiation by diverse chiral entities or by isotopically chiral promoters. [8,9] Kinetic and spectroscopic studies have provided much information about the nature of the autocatalytic process, and kinetic and computational modeling have contributed to our understanding. To date, however, neither experimental observations of intermediate species, nor evidence of the nature of the catalytic entity, have been reported.…”