Thermal and Photochemical Transformation of Conformational Chirality into Configurational Chirality in the Crystalline State

• Published in: Journal of the American Chemical Society Vol. 125; no. 14; pp. 4040 - 4041
• Main Authors: Chong, Kenneth C. W, Scheffer, John R
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 09.04.2003; Amer Chemical Soc
• Subjects: Chemistry; Chemistry, Multidisciplinary; Exact sciences and technology; General and physical chemistry; Photochemistry; Physical chemistry of induced reactions (with radiations, particles and ultrasonics); Physical Sciences; Science & Technology; ASYMMETRIC INDUCTION; SOLID-STATE; Chemical transformation; Conformational dynamics; Photochemical reaction; Thermal reaction; Tricyclic compound; Experimental study; Chiral auxiliary; Near ultraviolet radiation; Ammonium compound; Solid state reaction; Reaction mechanism; Ketoacid; Conformational equilibrium
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja029182i

Because they crystallize in chiral conformations in which abstraction of only one of two diastereotopic γ-hydrogen atoms is possible, salts formed between achiral keto-acids possessing the tricyclo[4.4.1.0]undecane ring system and optically pure amines undergo Norrish type II cleavage in the solid state in enantiomeric excesses as high as 95% at 98% conversion, following removal of the ionic chiral auxiliaries. Thermal enolene rearrangement of the same salts results in optical yields approximately half those observed for the photochemical reaction.