An-Xin Wu

Efficient Selective Formation of C‐C Single Bonds and C˭C Double Bonds by NBS‐Promoted Oxidative Coupling of β‐Keto Esters

Abstract A new application of NBS, which results in the oxidative coupling of β‐keto esters to selectively form C‐C single and C˭C double bonds, can be controlled by the amount of NBS and t‐BuOK employed. This methodology adds a new entry to C‐C single and C˭C double‐bond formation between active methylene groups under mild conditions with high selectivity.

5-Benz­yl-6-meth­yl-2-thioxo-2,3-dihydro­pyrimidin-4(1H)-one

Pyrimidine derivatives have received much attention due to their versatile uses. They have been widely used as tools to study biochemical systems and as chemotherapeutic agents (Koppel et al., 1961; Furberg & Petersen, 1972). As part of a general programme towards the synthesis of powerful chemotherapeutic agents, the title compound, (I), a new pyrimidine derivative, was synthesized. We report here the crystal structure of (I) (Fig. 1).

Dieth­yl 6,9‐dibromo‐1,4‐dioxo‐1,2,3,4,5,10‐hexa­hydro‐2,3,4a,10a‐tetra­aza­benzo[g]cyclo­penta­[cd]azulene‐2a,10b‐dicarboxyl­ate

The title compound, C18H18Br2N4O6, is an important interxadmediate for the synthesis of molxadecular clips. Interxadmolecular N—H⋯O hydrogen bonds form eight-membered rings. No π–π stacking is observed.

2,2,6,6-Tetra­methyl­piperidin-4-ol

The molxadecule of the title compound, C9H19NO, lies on a mirror plane. Interxadmolecular N—H⋯O and O—H⋯N hydrogen bonds are observed in the crystal structure.

Tetra­ethyl 2,2′‐(p‐phenyl­enedimethyl­ene)dimalonate

The molxadecule of the title compound, C22H30O8, contains a crystallographic inversion centre located at the middle of the benzene ring.

N,N′-Bis(N,N-dimethyl-p-toluidine)bis­(ethoxy­carbon­yl)glycoluril

In the title compound (systematic name: diethyl 4,8-dioxo-2,6-di-p-tolyl-1,3,5,7-tetraxadhydro-2,3a,4a,6,7a,8a-hexaxadazacyclopentaxad[def]fluorene-8b,8c-dicarboxylxadate), C28H32N6O6, the dihedral angles between the two fused five-membered rings in the glycoluril unit and between the two terminal benzene rings are 71.8u2005(2) and 88.5u2005(1)°, respectively.

2,6-Dibenzhydryl-8b,8c-diphenyl-2,3,5,6,8b,8c-hexa­hydro-2,3a,4a,6,7a,8a-hexa­aza-1H,4H-cyclo­penta­[def]fluorene-4,8-dione

The title compound, C46H40N6O2, is a glycoluril derivative. The molxadecule contains four fused rings, viz two nearly planar imidazole rings and two non-planar triazine rings. The triazine rings each have a chair conformation.

Dieth­yl 2,3-bis­(benzo[1,3]dioxole-5-carbon­yl)but-2-enedioate

The title compound, C24H20O10, is centrosymmetric about the central C=C bond, indicating that the molxadecule adopts a trans configuration and that the aromatic rings are parallel to each other. The crystal structure is stabilized by interxadmolecular C—H⋯O interxadactions.

Dieth­yl cis-1,2,3,4,5,10-hexa­hydro-6-iodo-1,4-dioxo-2,3,4a,10a-tetra­aza­benzo[g]cyclo­pent[cd]azulene-2a,10b-dicarboxyl­ate

The title compound, C18H19IN4O6, is a glycoluril derivative which contains four fused rings. An iodoxadbenzene ring is fused to a seven-membered ring linked to two of the N atoms from the separate rings of the glycoluril system. The structure is stabilized by interxadmolecular hydrogen bonds and π–π-stacking interxadactions.

2,6-Dibenzyl-8b,8c-diphenyl-2,3a,4a,6,7a,8a-hexa­azaperhydro­cyclo­penta­[def]fluorene-4,8-dione

The molxadecule of the title compound, C34H32N6O2, exhibits normal geometric parameters. The two terminal phenyl rings make a dihedral angle of 69.24u2005(2)° with each other. The crystal packing is stabilized mainly by van der Waals interxadactions.