Twisted Amides:  Synthesis and Structure of 1,6-Dipivaloyl-3,4,7,8- tetramethyl-2,5-dithioglycoluril

Abstract

[structure: see text] The 1,6-dipivaloyl derivative of 3,4,7,8-tetramethyl-2,5-dithioglycoluril (6) was prepared and the crystal structure determined by X-ray diffraction; 6 is a twisted amide in which severe ring strain and nonbonded interactions compel both pivaloyl groups to twist dramatically out of the ring plane. The amide oxygen atoms point in opposite directions with respect to the mean plane through the glycoluril core, and the bridgehead methyl groups are forced out of the symmetric syn geometry (eta = 30.5 degrees ). The structure of 7, a rearrangement product generated during synthesis of 6, was also determined by single-crystal X-ray diffraction.

New supramolecular organization for a glycoluril: chiral hydrogen-bonded ribbons

“…[2][3][4][5][6] Despite this intense interest in glycolurils, relatively few crystal structures are known. 1,[6][7][8][9][10][11] We present a series of three achiral glycolurils (1-3) that adopt an unusual, severely twisted conformation in the solid state to form chiral hydrogen-bonded ribbons (Fig. 1).…”

“…3). 11 The chemical origin of the twisting of glycolurils has remained elusive, although arguments have been proffered based on either steric interactions or differing electronics of the nitrogen atoms. 1,11,15 The twisting of the glycolurils observed here cannot arise simply from electronic differences between the nitrogens, since they are symmetric.…”

Biomimetic decarboxylative condensation between malonate and acetate units attached to a glycoluril template

“…This result is consistent with several observations of spontaneous hydrolysis under nonideal conditions, which we have made during our prior work with acylated glycolurils. This effect may be due to acyl group activation as the result of a twist around the amidic N-C bond, which we have observed to be substantial in X-ray crystallographic studies of related structures (21)(22)(23).…”

Crystal structure and Hirshfeld surface analysis of a new dithioglycoluril: 1,4-bis(4-methoxyphenyl)-3a-methyltetrahydroimidazo[4,5-d]imidazole-2,5(1H,3H)-dithione

“…A search of the Cambridge Structural Database (CSD, Version 5.39, February 2019) for thioglycoluril found two molecules similar to the title compound: 1,6-dipivaloyl-3,3a,4,6a-tetramethyltetrahydroimidazo[4,5-d]imidazole-2,5-(1H,3H)-dithione (refcode ADEMOL; Duspara et al, 2001) and 1,6-diacetyl-3,4,7,8-tetramethyl-2,5-dithiogylcoluril (SOLQIT; Cow, 1998). In both compounds, large polar groups are substituted on adjacent sides of the imidazole ring, resulting in steric hindrance and distortion of the C-N-C angles.…”