Synthesis of bridged carbocyclic systems related to diterpenes involving intramolecular cyclisation of diazomethyl ketones

The tricyclic dienediones 5,6 and 7 have been synthesised for entry into the ring systems of the tetracyclic diterpenes atisirene (1), phyllocladene (3) and hibaene (4) respectively.     

Acid-catalysed intramolecular cyclisation of diazomethyl ketones. synthesis of bridged tetracyclic systems related to diterpenes

Tetracyclo[10.3.1.0.^1,10.0.^2.7]hexadeca-2(7),9-diene-8,14-dione 7 and tetracyclo[10.2.2.0^1,100²⁷]hexadeca- 2(7),9-diene-8,13-dione 8 have been prepared through acid-catalysed intramolecular cyclisation of the diazomethyl ketones 19 and 25 respectively. The compound 7 is a skeletal representative of several tetracyclic diterpenes.     

Medium ring synthesis via intramolecular diels-alder reaction. I. The synthesis of bicyclo[6.4.O]dodecane systems

The regio- and stereocontrolled synthesis of $\text{cis}$-fused bicyclo[6.4.Oldodecane ring systems by the application of the Lewis acid-catalyzed intramolecular Diels-Alder reaction is described.     

Synthesis of 4-membered ring alkaloid analogues via intramolecular [2+2] cycloaddition involving keteniminium salt intermediates

We have developed a very straightforward method for the synthesis of 4-membered ring alkaloid analogues via intramolecular [2+2] cycloadditions. This involves the cyclization of a keteniminium salt in which an alkene is linked by the nitrogen atom, and where, the resulting cyclobutane iminium is reduced in a diastereoselective manner. Competition reactions have been performed to fully understand the features of this sequence. Moreover, DFT calculations have verified that the [2+2] cycloaddition step is driven by kinetic and not thermodynamic factors confirming all the experimental observations.     

Synthesis of heterocyclic systems involving [3,3]-sigmatropic rearrangements

Russian Chemical Bulletin - The review summarizes the data on the synthesis of heterocyclic compounds by means of [3,3]-sigmatropic transformations, which include the Fischer, Claisen, and Cope...     

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.     

吸热型碳氢燃料五环[6.3.1.02,7.03,5.09,11]十二烷的催化合成

吸热型碳氢燃料是为解决高超音速飞行器冷却难题而研制的一类新型燃料[1].其最突出的优点是作为性能优良燃料的同时,还能满足飞行器的冷却要求,可减小飞行器的体积和质量,提高飞行速度,是高超音速飞行器的理想燃料.其冷却及燃烧原理是:大分子碳氢燃料在进入燃烧室前吸收飞行系统产生的热量气化、再裂解为小分子,产物进入燃烧室燃烧并释放出吸收的热量,从而在对系统冷却的同时提高了能源的利用率,减少了高超音速飞行器的负载,满足了燃烧室壁面和机身温度控制等要求.因此,吸热型碳氢燃料已成为各国研发的热点,但目前研究多限于原油调配燃料的催化裂解和脱氢,对新燃料的合成报道较少[2,3].……     

Molecular complexity from aromatics: a novel, stereoselective route to tricyclo[5.2.2.0(1,5)]undecenones, tricyclo[6.2.2.0(1,6)]dodecenones, and [n.3.3]propellanes

A general stereoselective route to functionalized and substituted tricyclo [5.2.2.0(1,5)]undecenones, tricyclo[6.2.2.0(1,6)]dodecenones, and [3.3.3]- and [4.3.3]propellanes from simple aromatic precursors is reported. The methodology involves generation and cycloaddition of annulated cyclohexa-2,4-dienones with various acrylates followed by manipulation of the resulting tricyclic adducts, leading to functionalized tricyclo[5.2.2.0(1,5)]undecenones and tricyclo[6.2.2.0(1,6)]dodecenones endowed with a beta,gamma-enone chromophore. Photochemical reaction of the tricyclic chromophoric systems followed by reductive cleavage provided an efficient entry into propellanes.     

Synthesis and properties of 1,4,9-triazaspiro[5,5]undecane and 3,7,11-triazaspiro[5,6]dodecane

Bromination of 1-methylpiperidine-4-carboxaldehyde gave 4-bromo-1-methylpiperidine-4-carboxaldehyde hydrobromide which was used to synthesize 1,4,9-triazaspiro[5,5]undecane and 3,7,11-triazaspiro[5,6]dodecane. Cyanoethylation and alkylation with various alkyl halides gave their mono- and di-substituted derivatives. The side chain nitrile group was reduced and the hydrazide was obtained from the ester analog.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1673–1676, December, 1986.     

A highly efficient synthesis of bicyclo[n.3.1] ring systems by allene intramolecular cycloaddition: Tandem intramolecular [2+2] cycloaddition-[3,3]-sigmatropic rearrangement

A novel one-step construction of bicyclo[5.3.1]undecane skeleton via intramolecular cycloaddition of allenyl ethers is described.     

Synthesis of cyclopentano[c]-s -triazoles by the intramolecular ring transformation of 1,3,4-oxadiazoles

Cyclopentano[c]-s-triazoles were synthesized by intramolecular ring transformation starting from y-keto-l,3,4-oxadiazoles 5 and 9. The required functionality for this intramolecular reaction was established by (i) the reaction of lithiated 2-methyl-l,3,4-oxadiazole 4 with the methyl enol ether of α-bromo ketones followed by hydrolysis; (ii) reductive amination of γ-ketones 5 and 9 to further reorganized hydrazide 7 and y-amino-l,3,4-oxadiazole 9 with NaBH₃CN; and (iii) pyrolysis of 7 and γ at 280° (5 mmHg) to the cyclopentano[c]-s-triazoles 8 and 11. By the same treatment, the S-connected analogue 2 afforded the desired fused s-triazole 17.     

Density functional study of tricyclo[3,3,1,13,7]decane and tricyclo[3,3,1,13,7]decsilane and their halogen derivatives

The B3LYP/3‐21G* ab initio molecular orbital method from the Gaussian 94 computer program package was applied to study tricyclo[3,3,1,1^3,7]decane and tricyclo[3,3,1,1^3,7]decsilane molecules and their halogen derivatives (1,3,5,7‐tetrahalotricyclo[3,3,1,1^3,7]decane and 1,3,5,7‐tetrahalotricyclo[3,3,1,1^3,7]decsilane, C₁₀H₁₂X₄, and Si₁₀H₁₂X₄). The optimized structures of these compounds were obtained. Ionization potentials, HOMO and LUMO energies, energy gaps, heats of formation, atomization energies, and vibration frequencies were calculated. These calculations indicate that these molecules are stable and have T_d symmetry. Tricyclo[3,3,1,1^3,7]decsilane and its halogen derivatives (Si₁₀H₁₂X₄) are found to have higher conductivity than that of tricyclo[3,3,1,1^3,7]decane and its halogen derivatives (C₁₀H₁₂X₄). 1,3,5,7‐Tetraflourotricyclo[3,3,1,1^3,7]decane (C₁₀H₁₂F₄) and 1,3,5,7‐tetraflourotricyclo[3,3,1,1^3,7]decsilane (Si₁₀H₁₂F₄) were found to be the easiest compounds to form and the most difficult to dissociate of all 1,3,5,7‐tetrahalotricyclo[3,3,1,1^3,7]decane and 1,3,5,7‐tetrahalotricyclo[3,3,1,1^3,7]decsilane compounds, respectively. ©1999 John Wiley & Sons, Inc. Int J Quant Chem 72: 189–198, 1999     

Synthesis and Crystal Structure of 2,6,8,12-Tetraacetyl- 2,4,6,8,10,12-hexaazatetracyclo[5.5.0.05,9.03,11]dodecane

1 INTRODUCTION Hexanitrohexaazaisowurtzitane (HNIW or CL-20),the fourth generation in energetics, is the most power-ful explosive available for military applications inboth plastic bonded explosive (PBX) compositionsand propellant. To date, a number of nitrolyzable pre-cursors to CL-20 have been investigated, includingisowurtzitane cages substituted with acetyl, formyland nitroso groups and partly unsubstituted cages.Only the synthetic route of CL-20 using 2,6,8,12-te-traacetyl-2,4,6…     

Synthesis and characterization of polyimides based on novel tricyclo[6,2,2,02,7] dianhydride

3-Phenyl-tricyclo [6,2,2,0^2,7]dodeca-2,11-ene-5,6,9,10-tetracarboxylic dianhydride was prepared from 1,1-diphenyl ethylene and maleic anhydride in 1 : 2 mole ratio by [4 + 2]π Diels-Alder cycloaddition. The structure of the dianhydride was determined by mass spectroscopy, IR, ¹H-NMR, elemental analyses, and single crystal x-ray diffraction. The monomer was condensed with several diamines in N-methyl pyrrolidone or m-cresol. The polyamic acids and the polyimides synthesized had inherent viscosities in the range of 0.19–0.31 and 0.17–0.25 dL/g, respectively, measured in N-methyl pyrrolidone at 30°C. Both the polyamic acids and the polyimides were found to be soluble in m-cresol, N-methyl pyrrolidone, dimethylacetamide, dimethyl formamide, and dimethyl sulfoxide. The polymides showed a low degree of crystallinity from wide angle x-ray diffraction. Thermal analysis of these polyimides revealed that their glass transition temperatures (T_g) were in the 215–237°C range and they decomposed in two stages. The first-stage decomposition temperatures were almost the same in O₂ or N₂ atmospheres, but the polymers showed a better thermal stability in O₂ rather than in N₂ in the second stage. The mechanism of thermal degradation is discussed.     

New heterocyclic ring systems. XII. Synthesis of [1,4]thiazinocarbazoles

Five [1,4]thiazinocarbazoles have been synthesized from 6-, 7- and 8-amino-2H[1,4]benzo-thiazin-3(4H)ones by the Jaap-Klingemann reaction with 2-hydroxymethylenecyclohexanone followed by Fischer indolisation of the resulting hydrazones. The structures of the hitherto unknown ring systems have been confirmed by pmr spectral data.     

Synthesis of 3,5,7-Trioxapentacyclo[7.2.1.02,8.04,11.06,10]dodecane. A Novel Diacetal Trioxa-Cage

3,5,7-Trioxapentacyclo[7.2.1.0^2,8.0^4,11.0^6,10]dodecane, the parent compound of novel diacetal trioxa-cages, was synthesized from maleic anhydride cyclopentadiene adduct 1 by a four-step sequence. Attempts for the synthesis of monoaza dioxa-cage 12 failed. Ozonolysis of compound 9 in CH₂Cl₂-EtOH(1:1) at ?78°C followed by reduction with Me₂S gave 13 in 65% yield.     

Domino Reaction for the Synthesis of Highly Functionalized Triazatricyclo[6.2.2.01,6]dodecane

A simple and highly efficient protocol has been developed for the synthesis of triazatricyclo[6.2.2.0^1,6]dodecane-9,12-dione (TATCD) derivatives. Use of metal hydroxide catalyst in the presence of protic solvent plays a key role in these reaction transformations. Mechanistic studies specify that the proposed mechanism proceeds only via aldol reaction, condensation, cyclization, and dehydration to form the desired product. This current protocol provides several advantages such as use of a readily available precursor, consumption of less energy, short reaction time, moderate to good yields, and convenient workup.