Weak C—H...O and C—H...π hydrogen bonds and π–π stacking interactions in a series of four N′‐[(E)‐(aryl)methylidene]‐N‐methyl‐2‐oxo‐1, 3‐oxazolidine‐4‐carbohydrazides. Issue 8 (7th July 2015)

• Record Type: Journal Article
• Authors: Nogueira, Thais C. M.; Pinheiro, Alessandra C.; Wardell, James L.; Souza, Marcus V. N. de; Abberley, Jordan P.; Harrison, William T A
• Is Part Of: Acta crystallographica. Volume 71:Issue 8(2015:Aug.)
• Page Start: 647
• Page End: 652
• Publication Date: 2015-07-07
• Subjects: Crystallography -- Periodicals; Crystals -- Periodicals; 548.3
• DOI: 10.1107/S2053229615012450
• Languages: English
• ISSNs: 2053-2296

Abstract

<abstract abstract-type="main" xml:lang="en"> <title> <x xml:space="preserve">Abstract</x> </title> <p>Oxazolidin‐2‐ones are widely used as protective groups for 1, 2‐amino alcohols and chiral derivatives are employed as chiral auxiliaries. The crystal structures of four differently substituted oxazolidinecarbohydrazides, namely <italic>N</italic>′‐[(<italic>E</italic>)‐benzylidene]‐<italic>N</italic>‐methyl‐2‐oxo‐1, 3‐oxazolidine‐4‐carbohydrazide, C<sub>12</sub>H<sub>12</sub>N<sub>3</sub>O<sub>3</sub>, (I), <italic>N</italic>′‐[(<italic>E</italic>)‐2‐chlorobenzylidene]‐<italic>N</italic>‐methyl‐2‐oxo‐1, 3‐oxazolidine‐4‐carbohydrazide, C<sub>12</sub>H<sub>12</sub>ClN<sub>3</sub>O<sub>3</sub>, (II), (4<italic>S</italic>)‐<italic>N</italic>′‐[(<italic>E</italic>)‐4‐chlorobenzylidene]‐<italic>N</italic>‐methyl‐2‐oxo‐1, 3‐oxazolidine‐4‐carbohydrazide, C<sub>12</sub>H<sub>12</sub>ClN<sub>3</sub>O<sub>3</sub>, (III), and (4<italic>S</italic>)‐<italic>N</italic>′‐[(<italic>E</italic>)‐2, 6‐dichlorobenzylidene]‐<italic>N</italic>, 3‐dimethyl‐2‐oxo‐1, 3‐oxazolidine‐4‐carbohydrazide, C<sub>13</sub>H<sub>13</sub>Cl<sub>2</sub>N<sub>3</sub>O<sub>3</sub>, (IV), show that an unexpected mild‐condition racemization from the chiral starting materials has occurred in (I) and (II). In the extended structures, the centrosymmetric phases, which each crystallize with two molecules (<italic>A</italic> and <italic>B</italic>) in the asymmetric unit, form <italic>A</italic>+<italic>B</italic> dimers linked by pairs of N—H...O hydrogen bonds, albeit with different O‐atom acceptors. One dimer is composed of one molecule with an <italic>S</italic> configuration for its stereogenic centre and the other with an <italic>R</italic> configuration, and possesses approximate local inversion symmetry. The other dimer consists of either <italic>R</italic>, <italic>R</italic> or <italic>S</italic>, <italic>S</italic> pairs and possesses approximate local twofold symmetry. In the chiral structure, N—H...O hydrogen bonds link the molecules into <italic>C</italic>(5) chains, with adjacent molecules related by a 2<sub>1</sub> screw axis. A wide variety of weak interactions, including C—H...O, C—H...Cl, C—H...π and π–π stacking interactions, occur in these structures, but there is little conformity between them.</p> </abstract>