Forced twin-chair conformation in 7-benzoyl- and 7-phenylacetyl-r-2,c-4,t-6,t-8-tetraphenyl-3-thia-7-azabicyclo[3.3.1]nonanes with 1,3-diaxial phenyl groups in the piperidine ring: single- and double-layered supramolecular sheets built from C-H...O and C-H...pi(arene) hydrogen bonds.

The crystal structures of 7-benzoyl-r-2,c-4,t-6,t-8-tetraphenyl-3-thia-7-azabicyclo[3.3.1]nonane, C(38)H(33)NOS, (I), and r-2,c-4,t-6,t-8-tetraphenyl-7-phenylacetyl-3-thia-7-azabicyclo[3.

rac-5-Diphenylacetyl-2,2,4-trimethyl-2,3,4,5-tetrahydro-1,5-benzothiazepine and rac-5-formyl-2,2,4-trimethyl-2,3,4,5-tetrahydro-1,5-benzothiazepine.

rac-5-Diphenylacetyl-2,2,4-trimethyl-2,3,4,5-tetrahydro-1,5-benzothiazepine, C(26)H(27)NOS, (I), and rac-5-formyl-2,2,4-trimethyl-2,3,4,5-tetrahydro-1,5-benzothiazepine, C(13)H(17)NOS, (II), are both characterized by a planar configuration around the heterocyclic N atom. In contrast with the chair conformation of the parent benzothiazepine, which has no substituents at the heterocyclic N atom, the seven-membered ring adopts a boat conformation in (I) and a conformation intermediate between boat and twist-boat in (II). The molecules lack a symmetry plane, indicating distortions from the perfect boat or twist-boat conformations.

Sheets built from C-H...O and C-H...pi(arene) hydrogen bonds in (2RS,6SR)-N-diphenylacetyl-2,6-diphenylpiperidin-4-one and (2RS,3SR,5RS,6SR)-3,5-dimethyl-N-phenylacetyl-2,6-diphenylpiperidin-4-one.

In (2RS,6SR)-N-diphenylacetyl-2,6-diphenylpiperidin-4-one, C31H27NO2, (I), the piperidinone ring adopts an almost ideal twist-boat conformation, and the molecules are linked into sheets by a combination of one C-H...

Fast Equilibrium in N-(Ethoxycarbonyl)-r-2,c-7-diphenylhexahydro-1,4-diazepin-5-ones in Flattened Boat Conformations.

The preferred conformations of three N-ethoxycarbonyl derivatives of r-2,c-7-diphenylhexahydro-1,4-diazepin-5-ones 9-11 have been studied using NMR spectral techniques. The N(1),N(4)-bis(ethoxycarbonyl)-r-2,c-7-diphenylhexahydro-1,4-diazepin-5-ones 9 and 10 were found to prefer flattened boat conformations with fast equilibrium between two N-CO rotamers while 4-(ethoxycarbonyl)-t-3-isopropyl-r-2,c-7-diphenylhexahydro-1,4-diazepin-5-one (11) was found to prefer a chair conformation with the N-COOEt group locked in one rotameric state. Dynamic (1)H NMR studies have been carried out on the N(1),N(4)-bis(ethoxycarbonyl) derivatives 9 and 10, and the barriers for the N-CO rotation were found to be 49.