Sheets built from C-H ••• O and C-H ••• π(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-diphenyl-piperidin-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 center dot center dot center dot O hydrogen bond and one C - H center dot center dot center dot pi( arene) hydrogen bond. ( 2RS, 3SR, 5RS, 6SR)3,5-Dimethyl-2,6-diphenyl-N-phenylacetylpiperidin-4-one, C27H27NO2, (II), crystallizes with Z' = 2 in the space group P (1) over bar; the piperidinone rings adopt an almost ideal boat conformation in one of the molecules and a conformation between boat and twist - boat in the other. The molecules of ( II) are linked into sheets by a combination of five C - H center dot center dot center dot O hydrogen bonds and one C - H center dot center dot center dot pi( arene) hydrogen bond.