Condensed cyclic and bridged-ring systems : part 12: A novel synthetic route to 4-p-methoxyphenyl-bicyclo[ 2.2.2 ]octan-2-ones and some bicyclo [ 3.2.1 ] octane derivatives by acid-catalyzed intramolecula

The efficacy of a new acid-catalyzed intramolecular C-alkylation has been demonstrated by the synthesis of 1-methyl-4-$\text{p}$-methoxyphenylbicyclo [2.2.2] octan-2-one ($\text{5}$) and 4-$\text{p}$-methoxyphenylbicyclo [2.2.2] octan-2-one ($\text{6}$) from easily accessible starting materials. The carbinol $\text{20}$, derived from $\text{5}$, undergoes facile rearrangement leading to 1-$\text{p}$-methoxyphenyl-4-methyl bicyclo [3.2.1] oct-3-ene ($\text{22}$), which has been transformed to $\text{endo}$-1-$\text{p}$-methoxyphenyl-4-methylbicyclo [3.2.1] octan-3-one ($\text{25}$).     

A facile synthesis of strained bridgehead olefins by a gas-phase elimination reaction

A synthesis of bicyclo[3.3.1]non-1-ene $\text{1}$ and of a 10:1 mixture of bicyclo[4.2.1]non-1(8)-ene $\text{2}$ and bicyclo[4.2.1]non-1(2)-ene $\text{3}$ by gas-phase pyrolysis of the corresponding bridgehead acetates and chlorides is reported.     

Conversion directe des phospholes en dihydro-6,7 phosphepines dans la sphere de coordination du tungstene

In the presence of AlCl₃, [1-β-chloroethyl-3,4-dimethylphosphole]pentacarbonyltungsten($\text{1}$) rearranges into [1-chloro-3,4-dimethyl-6,7-dihydrophosphepin]pentacarbonyltungsten ($\text{3}$).     

Bridgehead nitrogen heterocycles from 2,4,6-triphenyl- pyrylium cation and thiosemicarbazide or thiocarbohydrazide

2,4,6-Triphenylpyrylium with thiosemicarbazide and thiocarbohydrazide, gives 2-pyrazolines $\text{3a}$ and $\text{3b}$ which undergo cyclization yielding pyrazolo(1,5-c]pyrimidine 5 and pyrazolo [2,3-d]-1,2,4-triazepine $\text{7}$ derivatives, respectively. Reaction of $\text{7}$ with phenacyl bromides gave 1,3-thiazolo[3,2-b]pyrazolo [2,3-d]-1,2,4-triazepin-4-iums $\text{10}$. Compound $\text{3a}$ on treatment with phenacyl bromides gave 1-(4'-aryl-thiazol-2'-yl)-2-pyrazoline derivatives $\text{6}$. Compound $\text{3b}$ reacts with acyl chlorides to give pyrazolo[1,5-c]pyrimidine derivatives $\text{14}$, and with aromatic aldehydes giving the 2-(Δ^2'1 pyrazolin-1-yl)-5-aryl-1,3,4-Δ²-thiadiazolines $\text{12}$ which were easily converted to the corresponding 2-(Δ²-pyrazolin-1-yl)-5-aryl-1,3,4-thiadiazoles $\text{13}$.     

Total synthesis of (+)-prelog-djerassi lactonic acid

Optically active Prelog-Djerassi Lactonic Acid $\text{1}$ was synthesized from D-glucal: the crucial point being the elaboration of the carboxylic group as shown in eq. 1 and 2 which involve the sequential process [i] asymmetric addition of methyl anion onto the hetero-olefin 2, [ii] trapping the carbanion intermediate $\text{3}$ [E=Li to SePh] and [iii] oxidative hydrolysis of $\text{3}$$\text{via}$ sila-pummerer rearrangement into $\text{4}$.     

An improved synthesis of [2.2.3]cyclazines from 3H-pyrrolizines

[2.2.3]Cyclazines are obtained in moderate yields by reaction of 3$\text{H}$-pyrrolizines bearing conjugative substituents (Ph or CO₂Me) with vinamidinium salts in the presence of strong bases. Syntheses of the previously unknown 2-phenyl-3$\text{H}$-pyrrolizine and 1-methoxycarbonylcyclopenta [$\text{h}$] [2.2.4] cyclazine are also described.     

Photo-oxygenations of 1H-azepine derivatives isolation and characterization of the [6+2] cycloaddition product

The reactions of 1H-azepine derivatives ($\text{1a-b}$ and $\text{4}$) with singlet oxygen gave the [6+2] cycloadducts ($\text{2a-b}$) and the [4+2] cycloadducts ($\text{3a-b}$ and $\text{5}$). The thermal and base-catalyzed rearrangements of the oxygen-adducts were investigated.     

Palladium-catalyzed cyclization reactions of 3-propargylthio 1,2,4-triazin-5(2h)-ones to thiazolo-1,2,4-triazinones

Selective transformation of 3-propargylthio-1,2,4-triazin-5(2H)-ones ($\text{1}$) to 6-methylene-6,7-dihydro-4H-thiazolo[2,3-c][1,2,4]-triazin-4-ones ($\text{2}$) and 3-methylene-2,3-dihydro-7H-thiazolo[3,2-b]-[1,2,4]triazin-7-ones ($\text{3}$) is performed under the conditions of Pd(II) salt or sodium hydroxide catalysis, respectively.     

3-methylthio-1,2-dithiolylium salts : Reaction with 4-hydroxy-6-methyl-2H-pyran-2-one and 4-hydroxycoumarin

The reaction of 4- and 5-aryl-3-methylthio-1,2-dithiolylium iodides with 4-hydroxy-6-methyl-2$\text{H}$-pyran-2-one and 4-hydroxycoumarin has been studied. 4-Substituted salts yielded 3-aryl-7-methyl-2-thioxo-2$\text{H}$,5$\text{H}$-pyrano [3,2-c]pyran-5-ones and 3-aryl-2-thioxo-2H,5H-pyrano[3,2-c]benzo[e]pyran-5-ones, respectively, whereas 5-substituted salts gave rise to 3-(5′-aryl-1′,2′-dithiol-3′-ylidene)-6-methyl-2$\text{H}$-pyran-2,4-diones and 3-(5′-aryl-1′,2′-dithiol-3′-ylidene)-2$\text{H}$-benzo [b]-pyran-2,4-diones.     

Palladium-catalyzed cyclization reactions : Unique synthesis of condensed thiazoles

The facile synthesis of 3-methylene-2,3-dihydro-5H-thiazolo-[3,2-c]pyrimidin-5-ones ($\text{9}$) has been performed by the catalytic action of a Pd(II) salt on 4-propargylthiopyrimidin-2(1H)-ones ($\text{6}$).Similar Pd(II)-catalyzed cyclization of 3-propargylthio-1,2,4-triazin-5(2H)-ones ($\text{10}$) gives 6-methylene-6,7-dihydro-4H-thiazolo[2,3-c](1,2,4]-triazin-4-ones ($\text{11}$) as a main product. 3-Methylene-2,3-dihydro-7H-thiazolo[3,2-b][1,2,4]triazin-7-ones ($\text{12}$), the regioisomers of $\text{11}$ are provided by a base-catalyzed cyclization of [ulbar 10].     

The [4.4.4.4]Fenestranes and[2.2.2.2]paddlane. Prospects for the realization of planar tetracoordinate carbon?

Semi-empirical (MINDO/3 and UNDO) MO calculations on highly strained planar tetracoordinate carbon candidates indicate the central carbons in $\text{cis}$- [4.4.4.4] fenestrane ($\text{1}$) to have pyramidal ($\text{1a}$) and in trans-[4.4.4.]fenestrane ($\text{2}$) to have distorted tetrahedral ($\text{2a}$) geometries. In [2.2.2.2]paddlane ($\text{3}$), the two central carbons are pentacoordinate. Each is nearly coplanar with four carbon neighbours; additionally, the two bridgehead carbons are connected by a single bond ($\text{3a}$).     

The octant rule. XVI1. COnformation and circular dichroism of syn and anti 2-methylbicyclo[3.1.0]hexan-3-ones,thujone and isothujone

(lS,5S)-exo-2(R)-Methylbicyclo[3.1.0]hexan-3-one ($\text{1}$) and (lS,5S)-endo-2(S)-methylbicyclo[3.1.0]hexan-3-one (2) were synthesized and their circular dichroism (CD) spectra run. Conformational analysis based on molecular mechanics calculations and Karplus equation analyses of vicinal H¦H NMR coupling constants indicate boat-like sofa conformations for both $\text{1}$ and $\text{2}$, with very little ring distortion from the symmetry of the parent bicyclo[3.1.0]hexan-3-one. The lone dissymmetric ψ-axial and ψ-equatorial methyl groups of $\text{1}$ and $\text{2}$, respectively, are both octant consignate. The natural product analogs of $\text{1}$ and $\text{2}$, (?)-3-isothujone ($\text{3}$) and (+)-3-thujone ($\text{4}$) were prepared and examined similarly. Their α-methyl perturbers dominate the CD n-π^★ Cotton effects.     

Acid catalyzed isomerization of bicyclic alkenes: a facile betweenanene synthesis

Isomerization of $\text{cis}$-bicyclo[10.8.0]eicos-1(12)-ene ($\text{1a}$) and $\text{cis}$-bicyclo[10.10.0]docos-1(12)-ene ($\text{1b}$) to [10.8]- and [10.10]betweenanene ($\text{2a}$ and $\text{2b}$) has been effected by sulfuric acid. In both cases, the betweenanene isomers were found to predominate at equilibrium (70/30 $\text{2a}$/$\text{1a}$ and 95/5> $\text{2b}$/$\text{1b}$).     

Reaction of neorl with thallium(III) perchlorate

Reaction of nerol ($\text{1}$) with thallium(III) perchlorate gave 6-oxabicyclo[3.2.1]octane derivatives ($\text{2}$) and ($\text{3}$), and 6,9-dioxabicyclo[3.3.1]nonane derivatives ($\text{4a–d}$) as the cyclization products.     

Pyridinethiones—II : Preparation of condensed pyridines related to 3-formyl-2(1H,-pyridinethione

Some condensed pyridines, isothiazolo[4,5-b]pyridine, 2-oxo-2$\text{H}$-thiopyranyl[5,6-b]pyridines, and thieno[3,2-b]pyridines, have been prepared from 3-formyl-2(1$\text{H}$)-pyridinethione or the 1-substituted precursors for this compound.     

v-Triazolines. part XXI. Spiro[bicyclo[2.2.1]hept-2-ene[54']1',2'.s'-triazole]derivatives from cyclopentadiene and 5-amino-4-methylene-v-triazolines

1R^*, 4R^*, 5S^*, 5'S^*-5'-Amino-1'-(4-nitrophenyl)-4',5'-dihydrospiro[bicyclo [2.2. 1]hept-2-ene[5.4]-1',2',3'-triazoles]$\text{2}$ have been obtained both by ?4 +2]-cycloaddition of cyclopentadiene to amino-methylene-1-(4-nitrophenyl)-4,5-dihydro-v-triazoles $\text{1}$ and by [3+2]-cycloaddition of 4-nitrophenylazide to 5-aminomethylene-2-norborenes $\text{4}$. The configuration has been fully established by X-ray crystallographic analysis. The course of the cycloaddition and the thermal behaviour of $\text{2}$ are discussed.     

The 185-nm photochemistry of 2,3-diazabicyclo[2.2.1]heptene and of its denitrogenation products bicyclo[2.1.0]pentane and cyclopentene

The 185-nm denitrogenation of 2,3-diazabicyclo[2.2.1]heptene ($\text{1}$) afforded bicyclo[2.1.0]-pentane ($\text{2}$) and cyclopentene ($\text{3}$) presumably via a “hot” cyclopentane-1,3-diyl diradical ($\text{8}$); 1,4-pentadiene ($\text{4}$) and methylenecyclobutane ($\text{5}$) were secondary products of the 185-nm photolysis of ($\text{2}$) and ($\text{3}$).     

The octant rule. XIV. synthesis and circular dichroism of α-exo and endo-deuteriobicyclo[3.2.1]octan-3-one and 6,6-dimethybicyclo[3.1.1]heptan-3-one

(1R,5S)-2S-Deuteriobicyclo[3.2.1]octan-3-one ($\text{1}$) and (1R,5S)-2R-Deuteriobicyclo[3.2.1]octan-3-one ($\text{2}$), prepared by diazomethane ring enlargement of (1S,4R)-2(exo)-deuteriobicyclo-[2.2.1] heptan-2-one and (1S,4R)-2(endo)-deuteriobicyclo[2.2.1]heptan-2-one respectively, both gave (?) n-π^* circular dichroism (CD) Cotton effects, Δε^max₂₉₄ = ?0.05 and Δε^max₂₉₄=?0.1, respectively, in hydrocarbon solvent. (1S,5R)-2S-Deuterio-6,6-diaethylbicyclo[3.1.1] heptan-3-one ($\text{3}$) and (1S,5R)-2R-deuterio-6,6-dimethylbicyclo[3.1.1] heptan-3-one ($\text{4}$), prepared from (-) myrtenal, both exhibited extraordinary vibrational fine structure for the n-π^* CD transitions observed in hydrocarbon solvent and oppositely?signed CEs, Δε^max₂₈₂=?0.01 and Δε^max₂₇₉=+0.01 respectively in CF₃CH₂OH solvent.     

En route to hexaaza-kekulene

As synthetic precursors of hexaaza-kekulene 1 the dibenzo[$\text{b,j}$]= [1,10] phenanthroline systems 2, 3, 4, 5 and 6 were prepared. From 6 via 7 a product was obtained for which the dodecahydrohexaaza-kekulene structure 8 is suggested on the basis of ¹H-NMR comparison with the dipyrido[3,2-$\text{c}$;=2′,3′-$\text{h}$]acridine (14) for which two syntheses are reported.     

Synthesis of (1s,5r)-karahana ether and (1s,5r)-karahana lactone,the optically active forms of unique monoterpenes wit

(1$\text{S}$,5$\text{R}$)-(-)-Karahana ether (8,8-dimethyl-2-methylene-6-oxabi-cyclo[ 3.2.1]octane) and (1$\text{S}$,5$\text{R}$)-(-)-karahana lactone (8,8-dimethyl-2-methylene-6-oxabicyclo [3.2.1]octan-7-one) were synthesized from ($\text{S}$)-3-hydroxy-2,2-dimethylcyclo-hexanone. The natural karahana lactone was shown to be almost racemic ($\text{ca}$. 1.3 % e.e.).