The use of the selective population inversion technique in the assignment of carbon-13 n.m.r. resonances in 3,6-epoxy-pentacyclo[6.2.1.02,7.04,10.05,9]undecane

Different applications of the selective population inversion technique in an n.m.r. study of 3,6-epoxypentacyclo-[6.2.1.0^2,7.0^4,10.0^5,9] undecane have been demonstrated. The intensity gain accompanying heteronuclear ¹³C—{¹H} experiments allowed the detection of fine structure due to long range C? H couplings otherwise hidden in normal proton coupled ¹³C spectra. Definite assignments of two very similar, directly bonded, C? H couplings within a methylene group have been made.     

Studies on hetero-cage compounds—VI : Transannular cyclizations in pentacyclo[6.2.1.0.2,70.4,1005,9]undecan-3,6-dione system

Several 4-oxa- and -aza-bird-cage compounds were prepared by transannular cyclizations of pentacyclo[6.2.1.0.^2,70.^4,100^5,9]undecan-3,6-dione (3). Diol derivatives of 3 cyclized to afford the corresponding 4-oxa-bird-cage derivatives such as 9, 16a and 16b. The corresponding 3-keto-6-ol derivatives (6, 10a and 10b) did not cyclize transannularly, while 3-imino-6-ol, 3-keto-6-amino, and 3- imino-6-amino type derivatives cyclized to afford 3-substituted 4-oxa- and -aza-bidr-cage compounds such as 12, 14 and 18. The transannular cyclization reactivity in the 3 system has been compared with that in the bicyclo[3.3.1]nona-3,7-dione system (1).     

Base-promoted rearrangement of cage α-haloketones—II : 12-oxa-3,5,9,10-tetrachlorohexacyclo[5.4.1.02,6.03,10.05,9.08,11]-dodecane-4-one

A synthesis of 12-oxa-3,5,9,10-tetrachlorohexacyclo[5.4.1.0^2,6.0^3,10.0^5,9.0^8,11]dodecane-4-one (6) from 4,4-dimethoxy-2,3,5,6-tetrachloropentacyclo [[5.4.0.0^2,6.0^3,10.0^5,9]undecane-8,11-dione (1) is described. Reaction of 6 with sodium hydroxide in refluxing benzene, toluene, or tetrahydrofuran affords 11-oxa-3,4,5-exo-6-tetrachloropentacyclo [[6.2.1.0^2,7.0^4,10.0^5,9]undecane-endo-3-carboxylic acid (7a, 80·2% yield). The corresponding reaction of 6 with refluxing aqueous sodium hydroxide solution affords 4,12-dioxa-8,11-dichlorohexacyclo-[5.4.1.0^2,6.0^3,10.0^5,9.0^8,11]dodecane-1-carboxylic acid (8a, 66·5% yield). A mechanism which accounts for the formation of 7a and 8a from 6 is presented.     

Evaluation of lipase from Candida rugosa in the resolution of endo-(±)-1,8,9,10,11,11-hexachloropentacyclo[6.2.1.13,6.02,7.05,9]dodecan-4-alcohol

endo-(±)-1,8,9,10,11,11-Hexachloropentacyclo[6.2.1.1^3,6.0^2,7.0^5,9]dodecan-4-ol (±)-7 and exo-(±)-1,8,9,10,11,11-hexachloropentacyclo[6.2.1.1^3,6.0^2,7.0^5,9]dodecan-4-ol (±)-4 have been prepared and the enantiomeric enrichment capacity of the lipase from Candida rugosa in the transesterification with vinyl acetate of these compounds was evaluated. It was verified that the lipase recognize only the alcohol (±)-7, producing endo-(+)-1,8,9,10,11,11-hexachloropentacyclo[6.2.1.1^3,6.0^2,7.0^5,9]dodecan-4-yl acetate (+)-8 with ee >95% and conversion of 44% as the only product.     

Synthesis and Characterization of Diastereoisomerically Pure Tetracyclo[6.2.1.13,6.02,7]dodec‐9‐ene‐4‐carboxylic Acid Derivatives

The synthesis and detailed NMR analysis of diastereoisomerically pure samples of 4‐methyltetracyclo[6.2.1.1^3,6.0^2,7]dodec‐9‐ene‐4‐carboxylic acid ( 2 ), tetracyclo[6.2.1.1^3,6.0^2,7]dodec‐9‐ene‐4‐carboxylic acid ( 6 ) and their tert‐butyl esters are reported. Mixtures containing two isomers of the methyl esters of these compounds were obtained by a twofold, sequential Diels‐Alder reaction between cyclopentadiene, and methyl methacrylate or methyl acrylate, respectively. Pure diastereoisomers of the acids were prepared by selective hydrolysis of their methyl esters.     

Synthesis, Structure, and Derivatives of endo-4-Aminomethyltetracyclo[6.2.1.13,6.02,7]dodec-9-ene

Synthesis was performed and structure studied of endo-4-cyanotetracyclo[6.2.1.1^3,6.0^2,7]dodec-9-ene prepared by reaction of a stereochemically uniform endo-5-cyanobicyclo[2.2.1]hept-2-ene with cyclopentadiene. By analysis of potential energy surface (PES) for reactions of endo-5-cyanobicyclo[2.2.1]hept-2-ene and the respective exo-stereoisomer with cyclopentadiene (in B3LYP/6-31G(d) approximation) the endo,exo-junction and anti-orientation of the methylene bridges in the bicyclic fragments of the adducts were shown to be preferable. Reduction of the tetracyclic nitrile with lithium aluminum hydride yielded endo-4-aminomethyltetracyclo-[6.2.1.1^3,6.0^2,7]dodec-9-ene whose geometry and conformational characteristics were studied by means of molecular mechanics method. Products were obtained from reactions of the tetracyclic amine with p-toluene-, p-chloro-benzene-, p-nitrobenzenesulfonyl chlorides, p-nitrobenzoyl chloride, succinic anhydride, mesityl and p-toluene-sulfonyl isocyanates, phenyl, p-toluenesulfonyl, and benzoyl isothiocyanates, p-nitrophenyloxirane, and N-(2,3-epoxypropyl)carbazole. A series of the amine derivatives was epoxidized with perphtahlic acid. The structure of compounds synthesized was confirmed by analysis of their IR spectra, ¹H, ¹³C, and two-dimensional NMR spectra, and additionally by calculation of the chemical shifts in ¹H and ¹³C NMR spectra by procedures GIAO and CSGT in PBE1PBE/6-31G^## approximation.     

Two-Step Synthesis of Heptacyclo[6.6.0.02,6.03,13.04,11.05,9.010,14] tetradecane from Norbornadiene: Mechanism of the Cage Assembly and Post-synthetic Functionalization

A selective and scalable two-step approach to the dimerization of norbornadiene (NBD) into its thermodynamically most stable dimer, heptacyclo[6.6.0.0^2,6.0^3,13.0^4,11.0^5,9.0^10,14] tetradecane, (HCTD) is reported. Calculations indicate that the reaction starts with the Rh-catalyzed stepwise homo Diels–Alder cyclisation of NBD into its exo-cis-endo dimer. Treatment of this compound with acid promotes its evolution to HCTD via a [1,2]-sigmatropic rearrangement. The assemblies of 7,12-disubstituted cages from 7-(alkyl/aryl) NBDs, as well as the selective post-synthetic C−H functionalization of the core HCTD scaffold at position C1, or positions C1 and C4 are described.     

Simple NMR method for assigning relative stereochemistry of bridged bicyclo[3.n.1]-2-enes and tricyclo[7.n.1.0]-2-enes

The stereochemistry of syn and anti-forms of bridged bicyclo[3.n.1]-2-ene, tricyclo[7.n.1.0]-2-ene (n=1-3) and bicyclo[4.3.1]dec-7-ene derivatives can be assigned from the ¹³C chemical shift difference of the double bond. Both syn-9-R-bicyclo[3.3.1]non-2-enes and syn-13-R-tricyclo[7.3.1.0^2,7]tridec-2(7)-enes have a large shielding difference between sp² carbons, while the corresponding anti-forms have a smaller one. In contrast, 8-R-bicyclo[3.2.1]oct-2-enes and 12-R-tricyclo[7.2.1.0^2,7]dodec-2(7)-enes have an inverse correlation. The reason of this specificity is the influence of the γ-gauche effect on the chemical shift of C(2) atom. The GIAO theory has been applied to investigate the ¹³C chemical shifts. The conformational equilibrium in the formamide group of 13-formylamino-tricyclo[7.3.1.0^2,7]tridec-2(7)-enes has been studied.     

Debenzylation of 2,6,8,12-tetraacetyl-4,10-dibenzyl-2,4,6,8,10,12-hexaazatetracyclo[5.5.0.03,11.05,9]dodecane

The debenzylation of 2,6,8,12-tetraacetyl-4,10-dibenzyl-2,4,6,8,10,12-hexaazatetra-cyclo[5.5.0.0^3,11.0^5,9]dodecane by catalytic hydrogenolysis in a mixture of HCOOH with other RCOOH (R = Me, Et, Prⁱ) is accompanied by the N-formylation of the liberated secondary amino groups. The alkaline hydrolysis of the obtained products makes it possible to remove the formyl groups with the retention of the acetyl groups.     

Synthesis of exo-3-amino-10-hydroxy-hexacyclo[10.2.1.0.0.0.0]pentadecane-5,7-diene-endo-3-carboxyclic acid and endo-3-amino-10-hydroxy-hexacyclo[10.2.1.0.0.0.0]pentadecane-5,7-diene-exo-3-carboxylic acid

Treatment of hexacyclo[7.4.2.0^1,9.0^3,7.0^4,14.0^6,15]pentadecane-10,12-diene-2,8-dione with aqueous sodium cyanide produced 2,8-dihydroxy-hexacyclo[7.4.2.0^1,9.0^3,7.0^4,14.0^6,15]pentadecane-10,12-diene-2,8-lactam and with sodium cyanide, ammonium chloride and ammonium hydroxide, 2-amino-8-hydroxy-hexacyclo [7.4.2.0^1,9.0^3,7.0^4,14.0^6,15]pentadecane-10,12-diene-2,8-lactam was obtained. 10-Hydroxy-hexacyclo [10.2.1.0^2,11.0^4,10.0^4,14.0^9,13]pentadecane-5,7-diene-3-one was converted into the corresponding aminonitrile and hexacyclo[10.2.1.0^2,11.0^4,10.0^4,14.0^9,13]pentadecane-5,7-diene-10-hydroxy-3-spiro-5′-hydantoin. Treatment of the latter with barium hydroxide produced exo-3-amino-10-hydroxy-hexacyclo [10.2.1.0^2,11.0^4,10.0^4,14.0^9,13]pentadecane-5,7-diene-endo-3-carboxylic acid. The isomeric endo-3-amino-10-hydroxy-hexacyclo[10.2.1.0^2,11.0^4,10.0^4,14.0^9,13]pentadecane-5,7-diene-exo-3-carboxylic acid was obtained from 3-cyano-3-ureido-hexacyclo[10.2.1.0^2,11.0^4,10.0^4,14.0^9,13]pentadecane-5,7-diene-10-ol.     

Heterodiamantane und strukturell verwandte Verbindungen. III.. Pentacyclische diäther der C11-reihe. 5, 13-Dioxapentacyclo-[6.5.0.02,6.03,12.04,9]tridecan, 4, 13-dioxapentacyclo [6.4.1.02,7.03,10.05,9]tridecan und 3, 10-dioxapentacyclo [7.3.1.02,7.04,12.06,11]tridecan

Heterodiamantanes and Structurally Related Compounds. Part III. The Pentacyclic C₁₁-Diethers 5, 13-Dioxapentacyclo [6.5.0.0^2,6.0^3,12.0^4,9]tridecane, 4, 13-Dioxapentacyclo [6.4.1.0^2,7.0^3,10.0^5,9]tridecane, and 3, 10-Dioxapentacyclo [7.3.1.0^2,7.0^4,12.0^6,11]tridecane In connection with the studies on heterodiamantanes and structurally related compounds the three novel pentacyclic diethers 3 – 5 were prepared starting from the cyclopentadienone dimer 6 . All four compounds have as common features a central carbocyclic 6-membered ring with four axial alkyl substituents and two oxygen functions in 1, 4 position. The required eleventh C-atom was introduced by dichlorocarbene addition either to 6 ( → 7 ) (Scheme 2) or to 29 ( → 28 ) (Scheme 4). Diether 3 was obtained by reduction of 26 (Scheme 2), a suitable precursor prepared either by intramolecular addition ( 24 → 26 ; Scheme 2) or substitution ( 30 → 26 , 31 → 26 ; Scheme 4), as well as by direct substitution ( 44 → 3 , 42 → 3 ; Scheme 5). Diether 4 was the product of a direct substitution ( 39 → 4 , 36 → 4 ; Scheme 5). The synthesis of diether 5 was achieved from the addition product 51 (resulting from the alcohols 47 and 48 ; Scheme 6). Diether 4 is the thermodynamically least stable of the three diethers 3 – 5 . It was easily isomerized to 5 on treatment with concentrated sulfuric acid in benzene whereas 3 and 5 remained unchanged under these conditions.     

Preparation and complete 1 H and 13C assignment of some pentacyclo[5.4.0.02,6.03,10.05,9]undecane‐8,11‐dione (PCUD) derivatives

The preparation of a number of alkyl and alkoxy derivatives of pentacyclo[5.4.0.0^2,6.0^3,10.0^5,9]undecane‐8,11‐dione derivatives utilising a cheap, practical, low energy, ‘green’, single‐pass continuous flow photochemical reactor is reported. Their ¹ H and ¹³C NMR spectra are fully assigned, revealing some general characteristics not previously reported for this class of compound, which should aid the assignment and prediction of the NMR spectra of PCUD derivatives. Copyright © 2012 John Wiley & Sons, Ltd.     

The reaction of 3,6-di-tert-butyl-1,2-benzoquinone and 3,6-di-tert-butylcatechol withtert-butyl hydroperoxide

Reaction of 3,6-di-tert-butyl-1,2-benzoquinone and 3,6-di-tert-butylcatechol withtert-butyl hydroperoxide in aprotic solvents leads to the generation of semiquinone (SQ^.H), alkylperoxy (ROO^.), and alkyloxy radicals. The reaction of SQ^.H and ROO^. produces 2,5-di-tert-butyl-6-hydroxy-1,4-benzoquinone, 3,6-di-tert-butyl-1-oxacyclohepta-3,5-diene-2,7-dione, and 2,5-di-tert-butyl-3,6-dihydroxy-1,4-benzoquinone. The radical generated from solvent attacks SQ^.H at position 4 with C−C bond formation. 4-Benzyl-2,5-di-tert-butyl-6-hydroxycyclohexa-2,5-diene-1-dione produced in this way is transformed into 4-benzyl-3,6-di-tert-butyl-1,2-benzoquinone under the reaction conditions. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 943–946, May, 1999.     

Synthesis of 3,11-Dioxatetracyclo[6.3.0.02,6.05,9]undecanes and 3,5,7-Trioxapentacyclo[7.2.1.02,8.04,11.06,10]dodecane

The synthesis of 3,11-dioxatetracyclo[6.3.0.0^2,6.0^5,9]undecanes has been accomplished from furans in a short sequence by iodine-induced cyclization reaction. The application of iodine-induced cyclization reaction for the synthesis of 3,5,7-trioxapentacyclo[7.2.1.0^2,8.0^4,11.0^6,10]dodecane itself was also demonstrated.     

13C NMR spectra of exo,exo- and exo,endo-stereoisomers of tetracyclo[6.2.1.02,7.13,6]dodecane

Conclusions The¹³C NMR spectra of the exo, exo- and exo, endo-isomers of tetracyclo[6.2.1.0^2,7.1^3,6]dodecane were studied. The chemical shift of the bridge carbon depends on the configuration of the geometric isomer and can be used as a criterion to identify the stereoisomers in polycyclic systems with a norbornane fragment.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 924–926, April, 1977.The authors express their gratitude to S. S. Berman and A. A. Petrov for supplying the compounds.     

The π-Anisotropy of the Double Bond of a syn-11-Oxasesquinorbornene Derivative.. Stereoselectivity of the Diels–Alder additions of (2-norborneno)[c]furan. Crystal structure of 11-oxa-endo-tetracyclo[6.2.1.13,6.02,7]-dodec-2(7)-ene-9,10-exo-dicarboxylic anhydride

The reaction of (2-norborneno)[c]furan ( 4 ) with maleic anhydride gave 11-oxa-endo-tetracyclo[6.2.1.1^3,6.0^2,7]dodec-2(7)-ene-9,10-exo-dicarboxylic anhydride ( 5 ) and, with methyl acetylenedicarboxylate, methyl 11-oxa-endo-tetracyclo [6.2.1.1^3,6.0^2,7]dodeca-2(7),9-diene-9,10-dicarboxylate ( 7 ). The syn-11-oxa-sesquinorbornenes 5 and 7 could be equilibrated with their cycloaddents. They are at least 2 kcal/mol more stable than the corresponding anti-sesquinorbornenes 6 and 8 . The structure of 7 was deduced from its spectral data, by epoxidation with air or a peracid to give the exo-epoxide 13 and by catalytic hydrogenation to give 14 . The structure of 5 was established by single-crystal X-ray diffraction. A dihedral angle of 163° was measured between the C(1,2,7,8) and C(2,3,6,7) planes in 5 . This important deviation from planarity for the C(2,7) double bond is attributed to (π, ω)-repulsive interactions that make the π-electron density of 2-norbornene and 7-oxa-2-norbornene derivatives preferentially polarized toward the exo-face. This finding is discussed in relation with the relative stability of the syn- and anti- 11-oxasesquinorbornenes and with the endo-stereoselectivity of the cycloadditions of the norbornenofuran 4 .     

Cyclization and rearrangements of diterpenoids. IX. Isomerization of (1R,2S,7S,10S,11R,12S,13S)-2,6,6,10,12-pentamethylpentacyclo[10.2.1.01,10.02,7.011,13]pentadecane by fluorosulfonic acid

It has been shown that the opening of the cyclopropane ring in (1R, 2S, 7S, 10S, 11R, 12S, 13S)-2,6,6,10,12-pentamethylpentacyclo[10.2.1.0^1,10.0^2,7.0^11,13]pentadecane takes place under the action of fluorosulfonic acid at all three carbon-carbon bonds, but at low temperatures the main isomerization product is (1R, 2S, 7S, 10S, 12S, 13S)-2,6,6,10,12-pentamethyltetracyclo[10.2.1.0^1,10.0^2,7]pentadecan-13-ol, and at the ordinary temperature the main products are (1R, 2S, 7S, 11S, 12R, 13R)-2,6,6,11,13-pentamethyltetracyclo[10.2.1.0^1,10.0^2,7]pentadeca-9-ene and (1S, 2R, 11S, 12R, 15R)-2,7,7,11,15-pentamethyltetracyclo[10.2.1.0^2,11.0^3,8]pentadeca-3(8)-ene.     

Thionation of the monoacetal of pentacyclo[5.4.0.0.0.0]undecane-8,11-dione

As part of a programme to synthesize thione derivatives with pentacyclo[5.4.0.0^2,6.0^3,10.0^5,9]undecane moieties it was decided to sulfurize the monoacetal 6 of pentacyclo[5.4.0.0^2,6.0^3,10.0^5,9]undecane-8,11-dione 2. Unexpectedly the diol 9 was isolated as the product.     

Molecular structure and hydrolytic stability amidinium salts derived from triazatricyclo[5.2.1.0]decane

Five amidinium salts have been prepared from triazatricyclo[5.2.1.0^4,10]decane (tacnoa) and characterised by mass spectrometry, NMR spectroscopy and X-ray crystallography. The X-ray structures revealed a long distance between the methine carbon and the ammonium nitrogen, viz., C-N distance 1.64-1.70 Å, cf. other C-N distances of 1.40-1.50 Å. An NMR study of 1-ethyl-4,7-diaza-1-azoniatricyclo[5.2.1.0^4,10]decane and 1-benzyl-4,7-diaza-1-azoniatricyclo[5.2.1.0^4,10]decane, confirmed that these amidinium salts hydrolyse in aqueous solution, the latter 60 times faster than the former. Tacnoa, which has C-N distances typical of single bonds, showed no evidence of hydrolysis after several days at 80 °C. Molecular modeling calculations indicate that the preferred gas phase structure of the salts is one where the positive charge is delocalised over the two secondary amines and the methine carbon. The calculated distance between this carbon and the ammonium nitrogen is 0.15-0.4 Å longer than in the crystal structure. The energy difference between the preferred gas phase and solid state conformations is 2 kJ mol⁻¹ and presents little barrier to nucleophilic attack of the methine carbon. Further analysis of the methine carbon geometry (C(7)) reveals that the bond angles in the benzyl salt are closer to those expected for an sp² centre than in the ethyl salt and that this could be the origin of the faster hydrolysis rate.     

Cyclization and rearrangement of diterpenoids. VI. Products of dehydration of (1R,2S,7S,10S,12S,13S)-2,6,6,10,12-pentamethyltetracyclo[10.2.1.01,10.02,7]pentadecan-13-ol by phosphorus oxychloride

It has been established that on the dehydration of (1R,2S,7S,10S,12S,13S)-2,6,6,10,12-pentamethyltetracyclo[10.2.1.0^1,10.0^2,7]pentadecan-13-ol with phosphorus oxychloride in pyridine a mixture of six substances is formed, from which three previously undescribed hydrocarbons have been isolated and identified: (1R,2S,7S,10S,11R,12S,13S)-2,6,6,10,12-pentamethylpentacyclo[10.2.1.0^1,10.0^2,7.-0^11,13]pentadecane, (1R,2S,7S,10S,12R)-2,6,6,10,13-pentamethyltetracyclo[10.2.1.0^1,10.0^2,7]pentadec-13(14)-ene, and (1R,2S,7S,10S,12R)-2,6,6,10-tetramethyltetracyclo[10.2.1.0^1,10.0^2,7]pentadec-13(16)-ene, these being based on two new carbon skeletons.Institute of Chemistry, Institute of Applied Physics, MSSR Academy of Sciences, Kishinev. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 203–211, March–April, 1988.