Dongxia Xing

Improved synthesis of racemic and optically active 4-hydroxycyclohex-2-en-1-one☆

Abstract A simple and inexpensive synthetic route which affords S -(−)-4-hydroxycyclohex-2-en-1-one ( 1a ) with high stereoselectivity and moderate enantioselectivity is reported. A key step in this procedure involves bakers yeast promoted reduction of 1α,4α,4aα,6,7,8aα-hexahydro-1,4-methano-naphthalene-5,8-dione ( 3 ), which affords optically active 8-hydroxy-1α,4α,4aα,8β,8aα-tetrahydro-1,4-methanonaphthalen-5(1 H )-one ( 4a , 80% de, 67% ee) in 32% yield. The absolute configuration of the 3,5-dinitrobenzoate ester of 4a (i. e., 5a ) was established unequivocally via single crystal X-ray structural analysis.

Synthesis of (Z)- and (E)-1,2-di(1-adamanyl)ethene and their respective reactions with dichlorocarbene☆

Abstract The synthesis of ( Z )- and ( E )-1,2-di(1-adamantyl)ethene ( 1a and 1b , respectively) is reported. Compound 1a reacts with dichlorocarbene to afford ( Z )-1-[3-(dichloromethyl)-1-adamantyl]-2-(1-adamantyl)ethene ( 2 , 27%), ( Z )-2,3-dichloro-1,3-di(1-adamantyl)propene ( 3 , 20%) and 1,1,2-trichloro-2-(1-adamantyl)chloromethyl-3-(1-adamantyl)cyclopropane ( 4 , 21%). The corresponding reaction of 1b produced (E)-1-[3- (dichloromethyl)-1-adamantyl],2-(1-adamantyl)ethene-( 5 , 34%) and ( E )-1,2-di[3-(dichloromethyl)-1-adamantyl]ethene ( 6 , 5%). The structures of 6, 7 , and 10 were established unequivocally via application of X-ray crystallographic methods.

(Z)- and (E)-1,2-di(1-adamantyl)ethene

Abstract A highly stereoselective four-step synthesis of ( Z )-1,2-di(1-adamantyl)ethene ( 1a , overall yield 64%) which employs methyl 1-adamantanecarboxylate ( 2 ) as starting material is described. Compound 1a is isomerized quantitatively to the corresponding E - isomer ( 1b ) by reaction with molecular iodine. Some features of the X-ray crystal structures of 1a and 1b are described.

Nucleophilic additions of primary and secondary amines to pentacyclo[5.4.0.02,6.03,10.05,9]undecane-8,11-dione

The crystal structures of three compounds formedvia nucleophilic attack of a heterocyclic secondary amine on PCU-8,11-dione, with the concomitant intramolecular attack of one keto oxygen on the carbon of the other ketone, are presented. In all three compounds, the bridging oxygen contains substantial p-character, and the bonds to the “attacking” nitrogen are significantly shorter than would be expected.

Synthesis and base promoted intramolecular nucleophilic reaction of 8-hydroxy-1,2,3,4-tetrachloro-9,9-dimethoxy-1α,4α,4aα,6,7,8β,8aα-hexahydro-1,4-methanonaphthalene-5(1H)-one

Catalytic hydrogenation of two substituted hexahydro-1,4-dimethanonaphthalene-5,8-diones results in reduction of the enedione carbon-carbon double bond with concomitant reduction of only one of the two chemically equivalent C=O groups. Reaction of one partially reduced product with base results in intramolecular addition to the carbon-carbon double bond.

Structure of a deaza dimer of 4-methyl-3H-1,2,4-triazole-3,5(4H)-dione

The title compound crystallizes in the monoclinic space group, P21/n; a = 9.0024(5), b = 5.8135(3), c = 15.2232(8) Å, β = 91.153(4)° Z = 4; and R = 0.050 based on 853 observed, unique reflections. The structure consists of two fused five-membered triazole rings, oriented relative to each other at 152°.

Stereospecific solid-state NaBH4-promoted reduction of 1-methylpentacyclo[5.4.0.02,6.03,10.05,9]undecane-8,11-dione

NaBH4 reduction of a cage dione proceeds in a stereospecific fashion to give theendo,endo-diol. This reactivity is related to the crystal structure.

Structure of 2-acetoxy-1,2-di(1-adamantyl)ethanone

The structure of 2-acetoxy-1,2-di(1-adamantyl)ethanone is reported. The steric requirements of the two adamantyl groups affect the structure in three ways—a slight elongation of the central bond, a small expansion of the angles about the central bond, and a conformation in which the C(sp2)-connected adamantyl group virtually bisects the large substituents attached to the sp3 carbon.

Highly stereoselective sodium borohydride promoted reduction ofendo-5-acetyl-1,2,3,4-tetrachloro-7,7-dimethoxynorborn-2-ene

Racemicendo-5-acetyl-1,2,3,4-tetrachloro-7,7-dimethoxynorborn-2-ene was stereoselectively reduced by sodium borohydride to give only theS,S orR,R diastereomers. The crystal structure of the product displays no unusual features.