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 ($\text{25}$).     

Chemistry of 4-membered cyclic nitrones (2, 3-dihydroazete 1-oxides); a novel one-step synthesis of N-acetoxy β-latams

2,3-dihydroazete 1-oxide $\text{1}$ reacts at room temperature with base, acid and lead tetraacetate to give the 5-hydroxyisoxazolidines $\text{4a}$ and $\text{4b}$, the 6H-1,2-oxazin-6-one $\text{7}$ and the N-acetoxy β-lactam $\text{8}$, respectively; the reaction with lead tetraacetate represents a simple one-step conversion of a 4-membered cyclic nitrone into a β-lactam.     

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.     

A reversible claisen rearrangement of 3-(3,3-dimethylallyl)-4-(3,3-dimethylallyloxy)quinolin-2-one; synthesis of buchapsine and loss of its 1,1-dimethylallyl group

Reversible Claisen rearrangement of 3-(3,3-dimethylallyl)-4-(3,3-dimethylallyloxy)quinolin-2-one ($\text{5}$) furnished the alkaloid, buchapsine ($\text{6}$), which readily lost the 1,1-dimethylallyl group; a mechanism for the cleavage reaction is proposed.     

Nitrogen bridgehead compounds part 12. The reaction of the ethyl 6-methyl-4--oxo-6,7,8,9-tetrahydro-4h-pyrido [1,2-a]pyrimidine-3-carboxylate with iminium chlorides.

The 9-formyl- and 9-ester derivatives /$\text{5}$,$\text{9}$/ can easily be prepared from the title pyrido [1,2-a]pyrimidine /$\text{1}$/ with iminium chlorides /$\text{2}$a,b/ via the 9-/dimethyliminium-methyl/-derivatives /$\text{3}$,$\text{6}$/.     

Carbocyclization reactions of 1-nitrocycloalkenes and cross-conjugated dienamines

Dodecahydro-8a-nitro-$\text{as}$-indacen-4 ( 2H )-one, dodecahy-dro-9a-nitro-4H-benz ¦e¦inden-4-one, dodecahydro-9b-nitro-5H-benz¦e¦inden-5-one and dodecahydro-4a-nitro-9 ( 1H )-phenanthrenone of $\text{cis}$-$\text{anti}$-$\text{cis}$ backbone are synthesized in quantitative yield by cycloaddition reaction of 1-nitro-cyclopent-1-ene and 1-nitro-cyclohex-1-ene with 1-( cyclopenten-1-yl )- and 1-( cyclohexen-1-yl )-1-( piperidin-1-yl )-ethenes respectively. The enamine intermediates are also isolated and characterized.     

Application of 2d-nmr spectroscopy in the structural determination of a new tobacco cembranoid

Proton-proton shift correlated 2D-NMR spectroscopy has been used to determine the structure of a new tobacco cembranoid as (1$\text{S}$,2$\text{E}$,4$\text{S}$,6$\text{R}$,7$\text{E}$)-4,6-dihy-droxy-2,7,12(20)-cembratrien-11-one (1). This assignment has been verified by chemical means.     

Cyclisatioh de diarylalcanes en milieu superacide : synthese de cetones tricycliques a methyle angulaire et mecanisme de leur isomerisation

Cyclisation of readily available diary1-1,2 ethanes $\text{1→4}$ proceeds in SbF₅,-HF at 0°C to yield tricyclic phenanthrenones $\text{5}$, $\text{6}$, $\text{7}$ and $\text{11}$ bearing an angular methyl group. This process implies the electrophilic attack of the more basic aromatic ring, reacting through its diprotonated form (on the oxygen and the meta carbon atom) on the second aromatic ring. Isomerization of these primary products may be observed to give ketones $\text{8}$, $\text{9}$, $\text{10}$ from $\text{3}$ and $\text{12}$ from $\text{4}$) and it has been demonstrated by the use of specifically deuterated $\text{3d}$ that it involves stereospecific 1,2 hydride (or deuteride) shifts, without exchange.     

Extrusion reactions-VI

4-(4-Quinazolinylthio)-butan-2-one and 3-(4-quinazolinylthio) propiophenone (4, R = CH₃, C₆H₅) with POCl₃ give 3-(3-oxobutyl)-4(3$\text{H}$)-quinazolone and 3-(2-benzoylethyl)-4(3H)-quinazolone (7, R = CH₃, C₆H₅, X = O) via S → N rearrangement followed by

conversion. Non-protic heterocyclic thioamides undergo similar oxidation.     

Synthesis of (2S,3R,1'R)-stegobinone,the pheromone of the drugstore beetle,with stereocontrol at C-2 and C-1'

(2$\text{S}$,3$\text{R}$,1'$\text{R}$)-Stegobinone [2,3-dihydro-2,3,5-trimethyl-6-(1'-methyl-2'-oxobutyl)-4H-pyran-4-one], the pheromone of $\text{Stegobium}$ $\text{paniceum}$ L., was synthesized with stereocontrol at C-2 and C-1' starting from ethyl ($\text{R}$)-3-hydroxybutanoate and methyl ($\text{R}$)-3-hydroxy-2-methylpropanoate. The dihydro-γ-pyrone ring of the pheromone was constructed by an intramolecular acylation followed by acid-catalyzed cyclization.     

Reaction of 5,5-diphenyl-2-thiohydantoin with 1,2-dibromoethane.crystal and molecular structures of 2,3-dihydro-6,6-diphenylimi-dazo-[2,1-b]-thiazol-5(6h)-one and 2,3-dihydro-5,5-diphenylimi-dazo-[2,-1-b]-thiazol-6(5h)-one and their reactivity

The crystal and molecular structures of the title isomeric compounds $\text{1}$ and $\text{2}$, obtained by intramolecular N,S--dialkylation of 5,5-diphenyl-2-thiohydantoin with 1,2-dibro-moethane, have been determined from X-ray diffractometer data. 2,3-Dihydro-6,6-diphenylimidazo-[2,1-b]-thiazol-5(6H)-one $\text{1}$ crystallizes in space group P2₁2₁2₁ with a=11.376(3), b=12,255(5), c=8.434(3) Å and Z=4. Crystals of $\text{2}$, containing one molecule of benzene, are monoclinic,space group P2₁/c with a=11.539(6), b=10.242(3), c=16.353(5) Å, β=95.45(5)° and Z=4. In both cases a planar geometry of the two fused five-membered heterocyclic rings was found. The selected bond lengths in $\text{1}$ and $\text{2}$, as well as those analogous imidazothiazinones $\text{3}$ and $\text{4}$, were used to calculate E_HOSE (Harmonic Oscillation Stabilization Energy). The problem of stability and chemical reactivity of compounds $\text{1}$ to $\text{4}$ is also discussed.     

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.).     

(4+2)-cycloaddition of nitroalkenes with ynamines; formation of a 4H-1,2-oxazine 2-oxide derivative

The formation of a thermally unstable (4+2)-cycloadduct, a 4H-1,2-oxazine 2-oxide derivative ($\text{1}$), from the reaction of 1-nitrocyclopentene with 1-phenyl-2-(1-pyrrolidinyl)acetylene has been proven by the structure elucidation of isoxazole derivative $\text{3}$ which results from thermal rearrangement and by the structure determination of the 1,3-dipolar adducts $\text{5}$ of $\text{1}$ with electron-deficient acetylenes.     

Studies on organophosphorus compounds—XXXVI: Simple new routes to phosphorins from 2-hydroxy-, 2-mercapto-, and 2-aminobenzoic acids and their derivatives

2-Hydroxybenzoic acid heated with 2,4 - bis(4 - methoxyphenyl) - 1,3,2,4 - dithiadiphosphetane - 2,4 -disulfide, 1, gave 2 - (p - methoxyphenyl) - 4$\text{H}$ - 1,3,2 - benzoxathiaphosphorin - 4 - one 2 - sulfide, 3, and its thio-analogue, 4, while its ethyl or phenyl esters gave 4 as the sole product. 2 - Mercaptobenzoic acid and its ethyl ester when heated with 1 produced 3$\text{H}$ - 1,2 - benzodithiole - 3 - one, 8, 3$\text{H}$ -1,2 - benzodithiole - 3 - thione, 9, and 2- (p - methoxyphenyl) - 4$\text{H}$ - 1,3,2 - benzodithia - phosphorin - 4 - one 2 - sulfide, 10. The reaction of 2 -aminobenzoic acid with 1 gave 1,2 - dihydro - 2 - (p - methoxyphenyl) - 4$\text{H}$ - 3,1,2 - benzoxaphosphorin - 4 - one 2 - sulfide, 12. Reactions of 1 with methyl 2 - aminobenzoate and 2 - aminobenzamides are described. Mechanistic considerations for the formation of the heterocyclic phosphorus compounds are presented.     

Studies on Chirality Transfer in the [2,3] Sigmatropic Rearrangement of Anions Derived from Trialkylstannylmethyl Allylic Ethers. Stereospecific Synthesis of (2R)-3-Benzyloxy-2-methylpropanol.

Virtually complete chirality transfer is observed in the [2,3] sigmatropic rearrangement of the anion derived from trialkylstanylmethyl ($\text{E}$)- or ($\text{Z}$)-allylic ethers.     

Synthesis of some 2-(heteroarylamino)benzimidazoles and their cyclization with phosgene

2-(Benzimidazol-2-ylamino)pyridine (4a) , 2-(benzimidazol-2-ylamino)pyrazine (4b) , and 2-(benzimidazol-2-ylamino)thiazole (4c) underwent a ring-closure reaction on treatment with phosgene affording 6H-pyrimido-[1′,2′:5,4][1,3,5]triazino[1,2-a]benzimidazol-6-one (1a) , 6H-pyrazino[1′,2′:5,4][1,3,5]triazino[1,2-a]benzimidazol-6-one (1b) , and 5H-thiazolo[2′,3′:4,5][1,3,5]triazino[1,2-a]benzimidazol-5-one (1c) respectively. The structure of these hitherto unknown heterocyclic systems was confirmed by their ir and mass spectra.     

The synthesis and rearrangement of epoxypyrones

The oxidation of 5-acyl-4-oxo-pyran-2-carboxylic acid esters $\text{1}$,$\text{2}$ to novel epoxypyrones and subsequent rearrangement to the previously inaccessible 6-substituted-5-hydroxy or 5-chloropyrones $\text{6}$ - $\text{9}$ are described.     

The ipso-nitration of p-cresol

The nitration of $\text{p}$-cresol by nitric acid in aqueous sulphuric acid involves ~40% $\text{ipso}$-substitution at C^Me. The 4-methyl-4-nitrocyclohexa-2,5-dien-1-one (I) formed undergoes an acid-catalysed rearrangement to 4-methyl-2-nitrophenol.     

π-Olefin-iridium-komplexe : X. Einschiebung von diphenylacetylen in die methylen—iridium-bindung von bis(η4-cyclooctadien-μ-methylen-iridium)

Bis(η⁴-cyclooctadiene-μ-methyleneiridium) reacts with acetylenes to yield various products. In the case of diphenylacetylene two compounds have been isolated from the reaction mixture and identified as a $\text{1}\text{1}$ adduct containing a μ-η¹, η³-1,2-diphenylallyl ligand (X-ray structure analysis), and as 1,2,4,5-tetraphenylbenzene.     

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.