Asymmetric Synthesis by Using Natural Sunlight under Absolute Achiral Conditions

Abstract

Irradiation of prochiral (E)-aroylacrylamide with sunlight gave single-handed pyrrolinone quantitatively and with an enantiomeric excess (ee) of over 99 % under absolutely achiral conditions. The phenomenon was explained by photoisomerization and reversible cyclization followed by dynamic crystallization involving deracemization.

Photoracemization‐Based Viedma Ripening of a BINOL Derivative

“…[18] Up to now,afew successful examples of resolution through dynamic crystallization of prochiral molecules racemizing under UV light starting from completely achiral conditions have been reported. [19,20] Here, we aim to extend the application of Viedma ripening to molecules racemizing by photocatalysis, and focus the attention on chiral BINOL derivatives. This class of compounds is widely used as catalysts in organic synthesis, as templates for chiral recognition and as building blocks for polymers and other molecules.…”

Chiral Symmetry Breaking of Spiropyrans and Spirooxazines by Dynamic Enantioselective Crystallization

“…Based on the above results, the chiral symmetry breaking of 1 – 3 by dynamic crystallization was examined (Figure ). First, dynamic crystallization was performed by the solvent evaporation method . Each spiro compound ( 1 – 3 ) was dissolved in methanol and crystallized by evaporating the solvent with stirring at room temperature.…”

“…Dynamic crystallization through racemization by ring‐opening and ring‐closing processes has been reported as a successful method for asymmetric amplification of isoindolinones and pyrrolinones having an aminal chiral center, but there are no reports of asymmetric amplification reactions by racemization of spirocyclic ring systems such as spiropyrans.…”

Making Use of the Direct Process Residue: Synthesis of Bifunctional Monosilanes

“…First, dynamic crystallization was performed by the solvent evaporation method. [8][9][10] Each spiro compound (1-3)w as dissolved in methanol and crystallized by evaporating the solventw ith stirring at room temperature. The solid-state circular dichroism (CD) spectrumo ft he resulting crystal was measured to analyze whether it converged preferentially to any optically active substance.W hen the crystallization was repeateds everal times, 2 and 3 consistently formed only ar acemic mixture, but 1 converged on one of the enantiomorphic crystals.…”

“…[5] Valuable successful examples have been reportedf or amino acid derivatives, [6] pharmaceutical materials, [7] and axially chiral materials. [8] Dynamic crystallization through racemizationb yr ing-opening and ring-closing processes has been reported as as uccessful method for asymmetrica mplification of isoindolinones [9] and pyrrolinones [10] having an aminal chiral center,b ut there are no reports of asymmetricamplification reactions by racemization of spirocyclic ring systems such as spiropyrans.…”