Teh-Chang Chou

Synthesis, reactions and thermal properties of endo-5,12: endo-6,11-dietheno-5,5a,6,11,11a,12-hexahydronaphthacene

Abstract The title compound 6 was synthesized in nine steps, starting from the Diels-Alder adduct 21 of ketomethanoethanonaphthalene 20 and p -benzoquinone, via 7,8-dimethylidene-diethenoanthracene 10 followed by Diels-Alder reaction with ( E )-bis(phenylsulfonyl)ethylene and aromatization. Photocyclization of 6 led to 32 via an intramolecular [2+2] cycloaddition. Hydrogenation and epoxidation of 6 gave the corresponding bis-benzo hydrocarbon 33 and bis-epoxide 34 . Bromination of 6 proceeded by transannular reaction to produce N -type exo, endo dibromide 35b and U -type exo, exo dibromide 36b . Compound 6 underwent thermal decomposition at 210 ± 5°C to form naphthalene and benzobarrelene.

Synthesis and Diels-Alder reactions of a facially dissymmetric tetracyclo-fused maleic anhydride with cyclic dienes

Abstract Facially dissymmetric maleic anhydride 1 is synthesized and undergoes Diels-Alder cycloadditions with cyclic dienes exclusively on the face syn to its etheno-bridges.

A FRAGMENTATION-PHOTOCYCLIZATION APPROACH TOWARDS HOMOSECOHEXAPRISMANE SKELETON

Abstract Birdcaged bicyclo[2.2.2]octene-1,4-diol 15 was prepared from Diels-Alder adduct of 5,5-dimethoxy-1,2,3,4-tetrachlorocyclopentadiene in five steps. This diol underwent DIB-promoted fragmentation to give tetracyclic dienes 16 and 17 . Intramolecular [2+2]photocyclization of 16 and 17 furnished hexacyclic cage compounds 18 and 19 having homosecohexaprismane skeleton.

Diels-Alder reactions of A cage-annulated cyclohexa-1,3-diene. Synthesis and crystal structure of A doubly-caged sterically-congested tetraol

Abstract The cage-annulated cyclohexa-1,3-diene 4a was synthesized form the Diels-Alder adduct of 5,5-dimethoxy-1,2,3,4-tetrachlorocyclopentadiene (DTCP) and 1,4-naphthoquinone by a [6 + 2]photocycloaddition. The cyclohexadiene substructure in 4a undergoes Diels-Alder cycloadditions with dienophiles, such as maleic anhydride, p-benzoquinone, 1,4-naphthoquinone and dimethyl acetylenedicarboxylate. The adduct 9 from the Diels-Alder reaction of 4a with p-benzoquinone was further elaborated to a C2v symmetric bis-caged tetraol 16 via oxidation of 9 with DDQ, followed subsequently by a [4+2]cycloaddition with DTCP, an intramolecular photoaddition, and dechlorination. Tetraol 16 displays strong intramolecular hydrogen bonding.

Facial Stereoselective Diels–Alder Cycloadditions of a Sesquibicyclo[2.2.2]octadiene-fused Maleic Anhydride with Exocyclic 1,3-Butadienes

Abstract The Diels–Alder cycloadditions of facially dissymmetric sesquibicyclo[2.2.2]octadiene-fused maleic anhydride 1 with exocyclic 1,3-butadienes have been studied. The reactions proceeded via syn-side (relative to the etheno-bridge in 1) attack of the diene upon 1.

A diels-alder cycloaddition-cope rearrangement approach to the construction of Cs and C2-symmetric hexacycloeicosatetraendiones

Abstract s - and C 2 -hexacycloeicosatetraendiones 2 are synthesized by a nine-step reaction sequence in overall yields of 15 – 20% from 1 serving as a cis-9, 10-dihydronaphthalene equivalent and 1,2,3,4-tetrachloro-5,5-dimethoxycyclopentadiene as a cyclopentadienone equivalent.

Synthesis and characterization of tetramethylene-syn-sesterbicyclo[2.2.2]octene

Abstract The synthesis of syn -sesterbicyclo[2.2.2]octene ( 7 ) bilaterally grafted by an exocyclic s - cis -butadiene moiety is achieved from 1,8,9,10-tetrachloro-11,11-dimethoxy- endo -tricyclo[6.2.1.0 2,7 ]undeca-3,5,9-triene ( 8 ) employing repetitive Diels–Alder cycloadditions between 1,3-cyclohexadiene, generated from p -benzoquinone, and diethyl fumarate or maleic anhydride as the exocyclic butadienyl equivalent, followed by subsequent transformation to the conjugated diene moieties. In comparison with the corresponding sesquibicyclo[2.2.2]octene 6 , the 1 H NMR demonstrates the anisotropic shielding effect operating within the three parallel laticyclic double bonds. However, the UV absorption of 7 shows less effect by the increase of laticyclic conjugated ethylene units.

Additions of Cyclopentadiene to a Dissymmetric Maleic Anhydride: Semiempirical Calculations of Their Thermodynamics and Kinetics

Abstract There are four conceivable products of the title addition, however only two of them have been prepared. MNDO, AM1, and PM3 quantum-chemical computations have been used in order to rationalize the observation. Activated complexes have been computed for the four possible additions and it was found that one C-C bond rather than two is created on the path from the reactants to the activated complex (the C-C bond varies between 1.70 and 1.87 A). Only one activated complex has been localized on each reaction path. The two types of products observed in experiment are computed to be both thermodynamically more stable and kinetically more feasible, and hence the computations agree with the observations.