Stereospecific synthesis of (5E)-PGE2 by palladium-catalyzed decarboxylative 2-alkenylation of 2-alkenyloxycarbonylated cyclopentanone derivative

(5$\text{E}$)-Prostaglandin E₂ methyl ester was synthesized from ($\text{R}$)-4-$\text{t}$-butyldimethylsiloxy-2-cyclopentenone by $\text{in}$$\text{situ}$ 2-alkenyloxycarbonylation of the organocopper conjugate-addition adduct followed by intramolecular palladium-catalyzed decarboxylative 2-alkenylation. A ($\text{E}$)-2-butenylated cyclopentanone derivative was obtained from either 2-[($\text{E}$)- or ($\text{Z}$)-2-butenyloxy-carbonyl]cyclopentanone derivative under the similar reaction condition.     

[2+2]-Cycloadditionen von vinylkationen

The vinylbromides $\text{1a}$ and $\text{1b}$ are allowed to react ith AgBF₄ and AgPF₆ in the presence of various olefins in CH₂Cl₂ as the solvent. Except for the reaction of cyclopentene with $\text{1a}$ all other olefins used, react with vinyl cation $\text{2}$ to form the cycloaddition products $\text{7}$, $\text{8a}$ and $\text{8b}$ in high yields.     

Photochemistry of N-aryl-2(1H)-pyrimidin-2-ones

Irradiation of N-aryl-2(1H)-pyrimidin-2-ones ($\text{3a}$-$\text{c}$) in a mixed benzene-alcohol solution afforded the products initiated by Type I cleavage, 1-(3-alkoxycarbonylamino-2-propene)-N-arylimines ($\text{4a}$-$\text{c}$, $\text{5}$, and $\text{6}$) in 45–51% yields.     

Polyalkoxy-2-aza-propenylium salts

The title compounds $\text{3}$, $\text{8}$, and $\text{10}$ have been synthesised by oxygen-alkylation of the alkoxy-substituted N-methylene amides $\text{1}$, $\text{6}$, $\text{7}$, and $\text{9}$ using triethyloxonium salt $\text{2}$. The stereochemistry of the new salts is discussed in terms of an competition between the 2-aza-allenium- and the 2-aza-allyl-cation structures (I) and (II).     

The resolution of racemic 2-alkyl-1-aminocyclopropane-1-carboxylic acids

Practical procedures for the resolution of racemic modification of (1$\text{R}$, 2$\text{S}$)-and (1$\text{S}$, 2$\text{R}$)-1-amino-2-ethylcyclopropane-1-carboxylic acid $\text{1a}$,$\text{b}$,(1$\text{R}$, 2$\text{S}$)- and (1$\text{S}$, 2$\text{R}$)-1-amino-2-methylcyclopropane-1-carboxylic acid $\text{2a}$,$\text{b}$, and (1$\text{R}$, 2$\text{R}$)- and (1$\text{S}$, 2$\text{S}$)-1-amino-2-methylcyclopropane-1-carboxylic acid $\text{3a}$,$\text{b}$ are described; the structures as $\text{1a}$,$\text{2a}$, and $\text{3a}$ were confirmed by X-ray-crystallographic methods.     

Cyclisierungen unter beteiligung von fluoridionen. 2. Mitteil. [1], [2]. 4.5-perfluor-1.3-dioxolane

4.5-Perfluoro-1.3-dioxolanes $\text{2}$ are available by reaction of 2(α-chloroalkoxy)perfluoro-carbonyl halides $\text{3}$ or -ketone $\text{9}$ with fluoride ions. A mechanism for the intramolecular ring- closure-reaction is proposed. Hydrogen atoms at C-2 in $\text{2}$ can be exchanged photochemically by chlorine. Starting from the 2-monochloro-derivatives $\text{16}$ the 2-monofluoro-4.5-perfluoro- 1.3-dioxolanes $\text{18}$ are formed by reaction with triethylamine- hydrofluoride.     

The reaction of 2-azaallenium salts with carbodiimides and tert-butyl isocyanide

2-Azaallenium salts $\text{1}$ react with diisopropyl carbodiimide to afford the formal dihydro-1,3-diazetium salts $\text{5}$. The structure of $\text{5c}$ has been confirmed by an X-ray diffraction analysis. With the carbodiimide $\text{2e}$ the tetraphenyl-2-azaallenium salt $\text{1a}$ reacts to give the guanidinium compound $\text{6}$.The diazetium salts $\text{5}$ react with further carbodiimide to afford the formal 2-azaallenium salts $\text{11}$. With tert-butyl isocyanide the 2-azaallenium salts $\text{1}$ undergo an Ugi reaction to yield the nitriles $\text{14}$.     

A facile synthesis of 2-(6-ethoxycarbonyl-2-cis-hexenyl)-4-hydroxy-2-cyclopentenone

The title compound $\text{1b}$, a key intermediate for PGE₂ elaboration, is readily available in nine steps from furfuryl alcohol. The crucial steps include the exclusive formation of $\text{6a}$ from $\text{5}$ and the subsequent intramolecular Aldol condensation to $\text{2b}$.     

Syntheses and thermal reactions of 2-alkyl(or aryl)-1-benzoyl-3,4-dihydro-2-thianaphthalenes

1-Benzoyl-2-methy1-3,4-dihydro-2-thianaphthalene ($\text{4a}$) underwent novel intermolecular 1,4-rearrangement in refluxing toluene to give an enol ether $\text{5a}$, while rearrangement of 2-phenyl derivative $\text{4e}$ proceeded intramolecularly in refluxing xylene to afford a 1,4-rearranged enol ether $\text{5b}$. On the other hand, ylides $\text{4a–e}$ were refluxed in alcohols to afford some ring-opened products $\text{10–12}$.     

Yield of I(2Psol:12) in the photodissociation of CH2I2

The production of I(²P_{$\text{1}\text{2}$}) in the photolysis of CH₂I₂ has been studied optoacoustically at excitation wavelengths between 365.5 and 247.5 nm. Bands found at 32200 and 47000 cm^?1 correlate with I(²P_{$\text{3}\text{2}$}) whilst those at 34700 and 40100 cm^?1, which correlate with I(²P_{$\text{1}\text{2}$}), give final ²P_{$\text{3}\text{2}$}/²P_{$\text{1}\text{2}$} ratios of 1.75 and 1.1, respectively, after curve crossing.     

Stereochemical studies 83 saturated heterocycles 76 : Preparation and conformational study of partially saturated 3,1-benzoxazines, 3,1-benzoxazin-2-ones and 3,1-benzoxazine-2-thiones

The $\text{cis}$- and $\text{trans}$-2-amino-4-cyclohexene-1-carboxylic acids $\text{1}$ and $\text{3}$ react with imidates to give the condensed-skeleton, bicyclic $\text{cis}$- and $\text{trans}$-pyrimidin-4-ones $\text{8}$ and $\text{9}$. The amino acids $\text{1}$ and $\text{3}$ were reduced to the $\text{cis}$-and $\text{trans}$-1, 3-aminoalcohoIs $\text{6}$ and $\text{7}$, which were cyclized by means of imidates to the bicyclic tetrahydro-4$\text{H}$-3,1-benzoxazines $\text{10}$ and $\text{11}$, or were converted, $\text{via}$ the corresponding carbamates $\text{14}$ and $\text{15}$ into the tetrahydro-4$\text{H}$-3,1-benzoxazin-2(1$\text{H}$)-ones $\text{16}$ and $\text{17}$. The 2-thioxo analogues $\text{18}$ and $\text{19}$ were prepared by cyclization of the dithiocarbamates obtained from the aminoalcohols $\text{6}$ and $\text{7}$ by treatment with carbon disulphide. The $\text{trans}$-aminoalcohol $\text{7}$ and its saturated analogue reacted with $\text{p}$-chlorobenzaldehyde to furnish the hexahydro $\text{13}$ and octahydro-4$\text{H}$-3,1-benzoxazine $\text{13a}$, respectively. ¹H and ¹³C NMR studies showed that, similarly to the earlier-investigated analogues containing oxygen or unsubstituted nitrogen at position 1, the synthesized $\text{cis}$ isomrs $\text{8}$, $\text{10}$, $\text{16}$ and $\text{18}$ occurred as the preferred conformer in the heterocyclic twist inverse form of $\text{N}$-inside type ($\text{quasiaxial}$ C₆-N bond) (B). In the $\text{trans}$ isomers containing a saturated C-2 atom ($\text{13}$ and $\text{13a}$), H-2 and H-6 are in $\text{cis}$ relative positions.     

4-thioxo-2-azetidinones by cycloaddition of thioketenes with isocyanates

The (2+2) cycloaddition of thioketenes $\text{1}$ with isocyanates $\text{2}$ yields 4-thioxo-2-azetidinones $\text{3}$, which can be hydrolyzed to the N-unsubstituted compound $\text{4}$ and thus used as versatile intermediates.     

Formation of benzo[a]phenoxazine derivatives by triethylphosphite-induced deoxygenation of 1-(2-nitrophenoxy) and 2-(2-nitrophenoxy)naphthalenes

Reaction of 1-(2-nitrophenoxy)naphthalene or its β-isomer $\text{7}$ with triethylphosphite produces benzo[a]phenoxazines $\text{8}$ and $\text{10}$, through the intermediate $\text{6}$.     

Acid-base reactions of 1,3,4-thiadiazolines and thiocarbonyl ylides; 1,3,4-thiadiazoline-2-spiro-2′-adamantane

The surprising formation of C₂₂H₃₂N₂S₂ from the title compound 1 at 45°C involves the interaction of the basic adamantanethione S-methylide ($\text{2}$) with its acidic precursor $\text{1}$, in the course of which the anion $\text{6}$ undergoes electrocyclic ring opening; the acid and base functions offer the clue to a prolific chemistry of the thiadiazoline $\text{1}$ and the thiocarbonyl ylide $\text{2}$.     

A facile one-pot preparation of 2-methyl-and 2-phenyl-4- fluoro-5-trifluoromethyl-6-methoxypyrimidine from methyl 2-hydryl-2-(F-methyl)-F-propyl ether

The title compounds were readily prepared in one-pot by phase-transfer reaction of a methanol adduct of 2-($\text{F}$-methyl)-$\text{F}$- propene with acetamidine or benzamidine in the presence of aqueous sodium hydroxide in CH₂Cl₂. Various 5-trifluoromethyl- pyrimidines were also synthesized $\text{via}$ nucleophilic substitution of the 4-fluorine of the title compounds.     

1,6-dithia-spiro[4.4]nonadiene aus 2-thiazolin-5-thionen

4,4-Dimethyl-2-phenyl-2-thiazolin-5-thione ($\text{4}$) reacts with 2,3-diphenylcyclopropenone ($\text{2a}$) at 145°C and with benzonitrilio-2-propanide ($\text{6}$) at room temperature to yield the 1,6-dithia-spiro[4.4]nonadienes $\text{5}$ and $\text{7}$, respectively.     

Photochemical (2+2)-cycloaddition of thioxanthenethione with some butatriene derivatives

Irradiation of thioxanthenethione $\text{1}$ with the alkyl- and alkoxysubstituted butatrienes $\text{2}$a-d gives the thietanes $\text{3}$a-d the cyclobutanethione $\text{6}$ is formed as a byproduct. Free radical addition of iC₃H₇SH to $\text{2}$a predominantly occurs via terminal attack of the thiyl radical on the π-system.     

Chemistry of ketene acetals II. A simple route to 2,2-dialkoxytetrahydrofurans, γ-butyrolactones, 2-(5H)-furanones and 2-alkoxy-4,5-dihydrofurans

2,2-Dialkoxytetrahydrofurans $\text{3}$ (a,b) have been synthesized from epoxides $\text{1}$ and ketene acetals $\text{2}$ using ZnCl₂ as a catalyst. By simple reactions compounds $\text{3}$ were converted into γ-butyrolactones $\text{5}$, 2-(5H)-furanones $\text{7}$ and 2-alkoxy-4,5-dihydrofurans $\text{8}$.     

Photolysis of a 2-tetbazeio from an enehydrazine

Photolysis of the 2-tetrazene $\text{1}$ gives the triazole $\text{2}$ by homolysis of one single N,N-bond. The formation of the other products $\text{4}$ – $\text{13}$ can be rationalized by regarding the aza-allyl radical $\text{3}$ as a common precursor.     

Transposition des oximies de la 2H-naptho [1,8-bc] pyrannone-3 et de la 2H-benzo [b] furannone-3

Refluxing the oximes ($\text{2}$) of naphtho-[1,8-bc] pyran-3(2H)-one and ($\text{6}$) of 3 (2H)-benzofuranone with alcoholic hydrogen chloride give the corresponding α-alkoxy-ketones $\text{3}$, $\text{4}$, $\text{5}$ and α-chloroketone $\text{7}$ respectively. This transformation appears to be related to the acid conversion of N-aryhydroxylamines to o. and p. substituted anilines (BAMBERGER réarrangement.