Peri-bridged naphthalenes. 4. chalcogen-bridged acenaphthylenes

Three new electron donors, acenaphtho[5,6-$\text{cd}$]-1,2-dithiole ($\text{1}$), acenaphtho[5,6-$\text{cd}$]-1,2-diselenole ($\text{2}$), and acenaphtho[5,6-$\text{cd}$]-1,2-ditellurole ($\text{3}$), can be prepared in 28%, 22%, and 14% yields respectively by reaction of the elemental chalcogens (S, Se, Te) with 5,6-dilithioacenaphthylene ($\text{4}$). Compound $\text{4}$ is generated by treatment of 5,6-dibromoacenaphthylen ($\text{5}$), for which a convenient preparation is described, with $\text{n}$-butyllithium (2 equiv.) in THF at ?78°C.     

Oxygenated limonene analogs. Preparation of tetramethylated carvone and carveols via regiocontrolled opening of tetramethyllimonene oxide.

Regioselective opening of trans epoxide $\text{2}$ gave $\text{endo}$ and $\text{exo}$ tetramethylated $\text{trans}$ carveols $\text{3t}$ and $\text{4t}$ respectively, which were oxidized to tetramethylcarvone ($\text{5}$) and its unstable exocylic isomer $\text{6}$; reduction of $\text{5}$ with DIBAH gave tetramethylated $\text{cis}$ carveol $\text{3c}$ exclusively, whilst analogus reduction of $\text{6}$ produced an epimeric mixture of $\text{4c}$:$\text{4t}$=85:15.     

Synthetic studies on β-lactam antibiotics. Part 16. synthesis of 1-carba-2-penem-3-carboxylic acid esters from penicillins utilizing a carbon-carbon coupling reaction

Allylazetidinones $\text{9}$, $\text{10}$, prepared by coupling of allylcoppers $\text{8}$ with chloroazetidinones $\text{6}$, $\text{7}$, were converted into carbapenem esters $\text{16}$, $\text{28}$–$\text{31}$ using an Emmons-Horner reaction to introduce the 6-side chain and an intramolecular Wittig reaction to form the carbapenem ring system.     

On the stereochemistry of photoaddition between α,β-unsaturated ketones and olefins. III.

The α,β-unsaturated ketone $\text{1}$ yields with allene the photocycloadduct $\text{3}$ predicted by our empirical photoaddition rule and the byproduct 7. The formation of this material may be rationalized by the sequence $\text{1}$ → $\text{4}$ → $\text{5}$ → $\text{6}$ → $\text{7}$. The isomeric ketone $\text{2}$ is unreactive under the same conditions, since α addition is prohibited by the rule and β addition is severely blocked.     

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.     

Phospha-S-triazines. VIII. Chloro-substituted diphospha-S-triazines

1,3-Bis(phenylchlorophospha)-5-perfluoroalkyl-2,4,6- triazine and the corresponding perfluoroalkylether analogue were synthesized by interaction of equimolar amounts of the respective amidines and imido-diphenyl-diphosphinic acid pentachloride. With additional quantities of amidine, 1,3-bis(phenylperfluoro-$\text{n}$-octanoylamidinophospha)-5-perfluoro- $\text{n}$-heptyl-2,4,6-triazine was obtained. The replacement of the chloro- by azido-groups in 1,3-bis(phenylchlorophospha)-5- perfluoro-$\text{n}$-heptyl-2,4,6-triazine proceeded readily. The mass spectral breakdown patterns of the chloro- and the amidino- substituted compounds were directly comparable to those of the bis(diphenylphospha)-s-triazines.     

Nucleophilic reactions of fluoroolefins.IV. Regioselectivity in the reactions of 1-phenylpentafluoropropenes with alkyllithium reagents

Reactions of 1-phenylpentafluoropropenes $\text{1a}$–$\text{c}$ with a number of alkyllithium reagents were investigated in detail. In all cases mixtures of 1-alkly-1-phenyltetrafluoropropenes $\text{2}$ and 2-alkyl-1-phenyltetrafluoropropenes $\text{3}$ were obtained. The ratio of products $\text{2}$ and $\text{3}$ is strongly influenced by both the electronegativity of the benzene ring substituents and the bulk of the alkyl group of the alkyllithium reagents. The increase of both of these factors favours formation of 2-alkyl-substituted alkenes $\text{3}$ with a reduced yield of 1-alkyl-substituted alkenes $\text{2}$. The influence of the benzene ring substituents in alkenes $\text{1}$ obeys the Hammett type correlation, while the influence of the bulk of the alkyllithium reagents exhibits good relationships with the Fellous and Luft scale of steric substituent constants E^x_s ; no linear correlation with other scales of steric constants was found. Overall regioselectivity, in the reaction of 1-phenylpentafluoropropenes $\text{1}$ with alkyllithium reagents, considering both the influence of the benzene ring substituents and steric factors, is expressed by the Pavelich-Taft type equation. Observed direction of the influence of the bulk of the alkyllithium reagents on the ratio of products $\text{2}$ and $\text{3}$ is interpreted in terms of steric strains influencing the geometry and free energy of the supposed intermediates involved in these reactions.     

Functionalized 2-azabicyclo[3.3.1]nonanes. IV. synthesis of the indolo[3,2-f]morphan system.

A short route to the 2-azabicyclo[3.3.1]nonan-7-one system is described. Condensation of 4-piperidones with diethyl 2-oxopropylphosphonate, followed by catalytic hydrogenation furnished the corresponding piperidylpropanones $\text{6}$ which were cyclized with mercuric acetate in acetic acid to the target target bicyclic ketones $\text{1}$. The Fischer indole synthesis from $\text{1}$$\text{a}$ afforded regioselectively the indole [3,2-f]morphan $\text{2}$, a new heteromorphan type.     

Intermolecular photoaddition involving 1,4-transfer of cyano group. 2. photoaddition of 6-cyano-1,3-dimethyluracil with acetylenic compounds

Wavelength dependent photoadditions of 6-cyano-1,3-dimethyluracil to phenylacetylenes are described. Photolysis with Prex-filtered light gave the fused cyclobutenes ($\text{3}$, $\text{9}$), whereas irradiation with 254-nm light afforded the rearranged adducts ($\text{5}$, $\text{11}$). The structures of the adducts were established by X-ray analyses.     

Circular dichroism of α-deuteriocarboxylic acids. Dissignate behavior of deuterium.

Positive n → π^* Cotton effects were shown by ($\text{S}$-2-deuteriopropionic acid, ($\text{S}$)-2-deuteriosuccinic acid, ($\text{R}$)-2-deuterioglycine and ($\text{R}$)-2-deuterioglycolic acid. Using an octant projection and conformational and chiroptical data, it can be shown that the deuterium substituent makes a dissignate contribution to the Cotton effect.     

Fluorine-containing amino acids and their derivatives. 6. An efficient synthesis of β-fluorinated alanines via fluorohalomethylation of aminomalonates

Aminomalonates, e.g., $\text{1}$ and $\text{2}$, smoothly reacted with difluoro- and chlorofluorocarbene to produce the adducts ($\text{3}$, $\text{4}$, and $\text{5}$) in good yields. These products were successfully converted to various versatile β-fluorinated alanine derivatives, i.e., β,β-difluoroalanine ($\text{6}$), N-acyl-β-fluorodehydroalaninate ($\text{7}$), and fluoropyruvic acid ($\text{8}$).     

Synthetic studies on β-lactam antibiotics. part 11. Completely stereocontrolled synthesis of 7α-unsubstituted 1-oxacephems from penicillins

A $\text{cis}$ intermediate $\text{3}$ was obtained by novel reductive cleavage of $\text{2}$, prepared from $\text{1}$ in $\text{6}$ steps including a new ester to ketone conversion. Regioselective bromination of $\text{3}$ followed by substitution and known conversions gave 1-oxacephems $\text{5}$.     

Selectivity variation in hydrolysis of phenyl acetates by simple modifications of β-cyclodextrin.

By reaction of β-cyclodextrin 6-monotosylate with alkyl mercaptans, 6-deoxy-6-alkylthio-β-cyclodextrins, $\text{2}$, $\text{3}$, and $\text{4}$, were prepared. Studies of the hydrolyses of $\text{m}$- and $\text{p}$-substituted phenyl acetates showed that the well-known meta-selectivity effect occurred with $\text{2}$, while none was observed with $\text{4}$. This variation in selectivity was due to a change in the catalytic rate constant caused by the substituent on β-cyclodextrin.     

Oxidative decarboxylation of [n.2.2]propellane carboxylic acids with lead tetraacetate. rearrangement approach to bicyclo [n.2.2.]bridgehead alkenes.

Oxidative decarboxylation of [n.2.2]propellane carboxylic acids ($\text{1a}$-$\text{c}$) with lead tetraacetate gave the bicyclic acetates ($\text{2b}$, $\text{c}$) having a bridgehead double bond and/or the tricyclic acetates ($\text{3a}$, $\text{b}$) in good yields. Vapor phase thermolysis of $\text{3a}$ or $\text{3b}$ afforded the bridgehead olefin $\text{2a}$ or $\text{2b}$ quantatively.     

Synthetic studies on β-lactam antibiotics. 18. Convenient,stereocontrolled synthesis of 3-methyl 7α-methoxy-1-oxacephems

Alcohols $\text{4}$ and $\text{8}$, prepared from $\text{3}$, underwent completely stereospecific etherification to give 1-oxacephams $\text{5}$ and $\text{10}$, which were converted into the 1-oxacephem nucleus $\text{1b}$ via $\text{6}$ and $\text{1c}$. Functionalization at C-3′ in $\text{6}$ and $\text{1c}$ was unsuccessful.     

Athrotaxis alkaloids. Part I. Alkaloids of A. Cupressoides

Eleven homoerythrina-type alkaloids ($\text{tilda1}$-$\text{tilda9}$, $\text{tilda11}$, $\text{tilda12}$) have been isolated from A. cupressoides (Taxodiaceae), of which six ($\text{tilda6}$-$\text{tilda9}$, $\text{tilda11}$,$\text{tilda12}$) had not previously been reported.     

Bifunctional chiral synthons via biochemical methods. : VI. C5 isoprenoid units.

Two methods for the preparation of the isoprenoid chiron $\text{4}$ have been developed using a microbial kinetic resolution of $\text{5}$ and an enantiotopically selective hydrolysis of $\text{7}$ catalyzed by PLE.     

1,4-diacetoxy-β-lactams. Reactions with nucleophiles

β-Lactam $\text{1}$ reacts with hetero nucleophiles under ring cleavage to give 2,2-dimethyl-3-oximinobutanoic esters $\text{6}$ and $\text{7}$. $\text{N}$-hydroxyazetidine $\text{5}$, the precursor of β-lactam 1, is prepared by a new method.     

Cycloaddition reactions of 1,3-benzothiazines - 6. Reactions of 1,3-benzothiazine derivatives with substituted acetyl chlorides

6, 7-Dimethoxy-2$\text{H}$-l,3-benzothiazine derivatives ($\text{1}$, $\text{8}$) react with substituted acetyl chlorides to give angularly condensed β -lactams ($\text{3a}$-$\text{d}$, $\text{10}$, $\text{11}$). The $\text{cis}$ compound $\text{11}$ was epimerised to the $\text{trans}$ derivative $\text{12}$. From the interaction of 2-phenyl-6,7-dimethoxy-4$\text{H}$-1,3-benzothiazine ($\text{7}$) and α -chloro-phenylacetyl chloride two stereoisomeric β -lactam derivatives ($\text{9a}$, $\text{b}$) were isolated, whereas in the other cases studied the reactions leading to β -lactams proved to be stereospecific. Analogous reactions of $\text{4}$-methyl-6,7-dimethoxy-2$\text{H}$-l,3-benzothiazine ($\text{5}$) furnished the enamides $\text{6a}$,$\text{c}$, $\text{d}$. Structures of the new compounds and configurations of the diastereomers were elucidated by IR and NMR spectroscopy.     

Electron-transfer photooxygenation. 8. dicyanoanthracene-sensitized photooxidation of ortho-dimethoxybenzene

Two cleavage products, $\text{cis,cis}$-dimethylmuconate ($\text{1}$) and $\text{trans,trans}$-dimethyl-muconate ($\text{2}$), are inefficiently produced in the 9,10-dicyanoanthracene (DCA) sensitized photooxidation of $\text{ortho}$-dimethoxybenzene ($\text{o}$-DMB) in polar solvents. An electron transfer mechanism is proposed in which superoxide ion (O^?₂0 combines with ortho-dimethoxybenzene to form a dioxetane (3), which cleaves to form ($\text{1}$). The initial products is $\text{1}$, which is rapidly converted to $\text{2}$ and other products under the conditions; $\text{no}$ cis-trans isomer is formed.