Gordon I. Fray

Intermediates for the synthesis of linear chains of 1,2:4,5-fused cyclohexa-1,4-diene rings and beltenes by repeated Diels–Alder reactions

A synthetic strategy for the preparation of chains of 1,2:4,5-fused cyclohexa-1,4-diene rings, both linear and cyclic (beltenes), based on the repetitive Diets-Alder cycloaddition of p-benzoquinone with a tetramethylene-ethane synthon (3,4-dimethylenetetrahydrothiophene 1,1-dioxide) is described. This route has been developed to yield 5,1 1-dihydroxy-4,6,7,9,10,12-hexahydro-1H,3H-anthracene[2,3-c:6,7-c′]dithiophene 2,2,8,8-tetraoxide 16, a potential precursor of a tricyclic doubly-exocyclic diene, and 7,10-bis(tert-butyldimethylsilyloxy)-1,4,5,6,11,12-hexahydronaphthacene-1,4-dione 22, a potential precursor for the double dienophile 5,6,11,12-tetrahydronaphthacene-1,4,7,10-diquinone, but the generation of these Diels–Alder components and their combination to form a [9]-beltene derivative has not been accomplished. The synthesis of linear derivatives has proceeded as far as a protected heptacyclic derivative, 7,16-diacetoxy-1,4,10,13-tetrakis(tert-butyldimethylsilyloxy)5,6,8,9,14,15,17,18-octahydroheptacene 25. The 1H NMR spectrum of this compound is unexpectedly temperature dependent.

Reactions of cyclo-octatetraene and its derivatives—IX: Cyclopentadienone adducts of tricyclok[4.2.2.02,5]deca-3,7-dienes and tricyclo[4.2.1.02,5]nona-3,7-dienes1

Abstract Tetracyclol[8.2.2.02,9.03,8]tetradeca-4,6,11-trienes 5 are produced from tricyclo[4.2.2.02,5]deca-3,7-dienes 1 by reaction with cyclopentadienones 2 (or equiv) followed by thermal decarbonylation. With tetraphenylcyclopentadienone, however, the product 5e rearranges under the conditions required for its formation to give the dihydrosemibullvalene 11. The rearrangement evidently proceeds via the cyclo-octa-1,3,5-triene 14, the ring-opening 5e→14 being facilitated by a phenyl-conjugation effect, uncovered in another series of experiments involving the reaction of cyclopentadienones with the tricyclo[4.2.1.02,5]nona-3,7-diene 16. Thus the tetraphenylcyclohexa-1,3-diene 18c undergoes ring-opening in refluxing xylene to afford the eyclo-octa-1,3,5-triene 21a, whereas the dimethyldiphenyl-analogue 18b resists valence isomerisation under these conditions.

Stereochemistry of the 1,2-photocycloadducts of vinyl ethers and benzene

Die Addukte aus Olefinen an Benzol (I) der allgemeinen Struktur (II) werden hinsichtlich ihrer Isomeren und deren Trennung untersucht.

The stereochemistry of 1,2-photocycloaddition of vinylic compounds to benzene

The stereochemistry of the 1,2-photocycloaddition of benzene to acrylonitrile, methyl acrylate, methyl methacrylate, methyl vinyl ketone, ethyl vinyl ether, butyl vinyl ether, 2,3-dihydropyran, and 2,3-dihydro-1,4-dioxin has been investigated. The evidence indicates that exo-1,2-adducts are formed exclusively from all these vinylic compounds except the acrylates and methyl vinyl ketone, which gave mixtures of exo- and endo-stereoisomers.

Reactions of cyclo-octatetraene and its derivatives. Part V. Addition of bromotrichloromethane, carbon tetrachloride, and thiophenol to tricyclo[4.2.2.02,5]deca-3,7-diene-9,10-dicarboxylic anhydride

The free radical addition of bromotrichloromethane and carbon tetrachloride to tricyclo[4.2.2.02,5]deca-3,7-diene-9,10-dicarboxylic anhydride (I) results in trans-addition to the cyclobutene double bond. The structures (VIa) and (VIb) proposed for the products are based on n.m.r. studies of the adducts and various related compounds; by analogy structure (VIc) is suggested for the thiophenol adduct.

Reactions of cyclo-octatetraene and its derivatives - X: 1,2,3,8-Tetraphenylcyclo-octatetraene and 2,3,4,5-tetraphenylcyclo-octa-1,3,5-triene

Abstract The reaction of tetracyclone 1b with the cyclo-octatetraene-dimethyl acetylenedicarboxylate adduct 2 at ca . 110° produces, in addition to the exo [4+2] Π cycloadduct 3b (49%), 1,2,3,8-tetraphenylcyclo-octatraene 5 (11%), together with the diketone 11 (5%). In a similar reaction with the esterified cyclo-octatetraene-maleic anhydride adduct 13a , the major product 14 (82%) is accompanied by the cyclohexa-1,3-diene 15 and the dihydrosemibullvalene derivative 16 . Thermolysis of 3b at ca . 145° leads to the cyclobutene 12 ., which on catalytic hydrogonation followed by decarbonylation at 180°–190° gives 2,3,4,5-tetraphenylcyclo-octa-1,3,5-triene 19 . Attempted thermal conversion of 19 into a dihydrosemibullvalene failed.

Synthesis of (1S*, 2S*, 3S*, 4S*, 5S*, 6S*, 7S*, 8S*)-1,2,7,8-tetrachlorotricyclo[4.2.0.03,8]octane-4,5-dicarboxylic acid. Novel entry into the C2-bissecocubane system

Photocaging of the known Diels–Alder dimer of 2,3-dichlorocyclopentadienone, compound 1, followed by alkali-induced double ring-cleavage of the resulting caged diketone rac-2 or its dihydrate rac-3, led to the title tetrachloro dicarboxylic acid rac-5, thus affording a novel entry into the inherently chiral tricyclo[4.2.0.03,8]octane (C2-bissecocubane) system. Electrolysis of the disodium salt of rac-5 gave the tetrachloro alkene rac-14, from which other derivatives were obtained by standard methods.