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 $\text{10–12}$.     

Formal total synthesis of β-pipitzol

(±)-$\text{O}$-methylperezone ($\text{1b}$) was obtained by selective oxidative demethylation of (±)-leucoperezone trimethyl ether ($\text{4a}$). Compound ($\text{4a}$) was prepared by condensation of 2,3,5-trimethoxytoluene ($\text{5e}$) with 6-methyl-5-hepten-2-one, followed by reductive removal of the tertiary alcohol. The aromatic precursor $\text{5e}$ was prepared in four steps from 2,3-dimethoxytoluene ($\text{5a}$) and, alternatively, in three steps from 5-bromoveratraldehyde ($\text{6a}$). Racemic $\text{1b}$ and $\text{4a}$ were directly compared with the optically active molecules prepared from natural R(-)-perezone ($\text{1a}$).     

Photocyclization of n-[ω-(cycloalken-1-yl)alkyl]-and n-[ω-(inden-3-yl)alkyl]phthalimides : Synthesis of spiro-nitrogen multicyclic systems

Photolysis of the N-[ω-(cycloalken-1-yl)alkyl]phthalimides 6b-$\text{e}$ in each case gave a pair of stereoisomers of spiro-nitrogen multicyclic systems (9b-$\text{e}$) in moderate yields, whose stereochemistry was determined by means of chemical and spectroscopic analyses. Similarly, in N-[ω-(inden-3-yl)alkyl]-phthalimides (8), spiro-nitrogen macrocycles up to 13-membered 13a-$\text{c}$ were obtained in good yields     

Unprecedented rearrangements via allenes as π-participants in α-acyliminium ion cyglisations

Upon HCOOH reaction of ethoxylactams $\text{1a}$-$\text{1d}$ the terminally unsubstituted allenes $\text{1a}$ and $\text{1d}$ underwent a [3,3] sigmatropic rearrangement. The dimethyl allenes 1b and 1c afforded only products from an α-acyliminium ion cyclisation.     

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.     

Structure de la gouregine,alcaloïde orginal apparente aux cularines

The structure of guoregine, a new isoquinoline alkaloid from $\text{G}$$\text{u}$$\text{a}$$\text{t}$$\text{t}$$\text{e}$$\text{r}$$\text{i}$$\text{a}$$\text{o}$$\text{u}$$\text{r}$$\text{e}$$\text{g}$$\text{o}$$\text{u}$, Annonaceae, has been deduced by spectral analysis and confirmed by an X-ray structure determination. It is the first member of a new class of cularine-related alkaloids (α-$\text{g}$$\text{e}$$\text{m}$-dimetyltetradehydrocularines).     

N-cyano-α-diazoimine - synthese und umlagerung zu n-cyanoketeniminen

Cyanazide reacts selectively with the acylmethylenphosphoranes $\text{6a}$–$\text{e}$ under the formation of triphenylphosphanoxide and the N-cyano-α-diazoimines $\text{5a}$–$\text{e}$. Photolytically the diazo compounds are transformed into the N-cyanoketenimines $\text{13}$, which are trapped as imidoesters ($\text{14a}$–$\text{e}$) by the addition of methanol.     

Reactions of β-substituted amines-IV: Kinetics and stereochemistry of the thermal to (r) 3-chloro-1-ethylpiperidine,and the stereo-chemical course of their reactions with nucleophiles

The rate of the thermal rearrangement of (S) 2 chloromethyl-1-ethylpyrrolidine [(S)-1a] to (R)-3-chloro-1-ethylpiperidine [(R) 2a] has been examined at three temperatures in benzene by PMR and polarimetry. The rearrangement was shown to be completely stereospecific and to obey a simple first order rate law. The calculated E_a ΔH3 and ΔS3 were 22 ± 2 $\text{kcal}\text{mole}$ (25°), 21 ± 2.5 $\text{kcal}\text{mole}$ (25°) and - 10 ± 2 e.u. (0°K) respectively. The effect of solvents having differing dielectric constants was also studied. A transition state 9'a and an ion pair intermediate 3a are suggested for the rearrangement. The stereochemical course of the reactions of (S)-1a, (R)-2a and (S)-2a with hydroxide and methoxide ions have been shown to be 100% stereospecific with an uncertainty of about 1%. The absolute configurations of all optically active reactants and products [(S)- and (R)-4a, (S)-4b (R)- and (S)-5a, (R)-5b, (S,S')-6a, (S,R')-7a and (R,R')-8a] were established by chemical correlations with known compounds or by ORD and chemical inference. The ring opening of both the primary and secondary aziridinium ion positions of 1-azonia-1-ethylbicyclo [3.1.0]hexane [(S)-3a] by nucleophiles proceeds entirely by S_N2 processes. The conversion of (R)-1-ethyl-3-hydroxypiperidine [(R)-5a] to (S)-2a. HCl with thionyl chloride in chloroform proceeds by inversion with 4.8% racemization, whereas the thermal rearrangement of (S)-1a to (R)-2a occurs with complete retention of absolute configuration.     

A convenient synthesis of flindersine,atanine and their analogues

A new synthesis of the pyranoquinolone alkaloids flindersine ($\text{8a}$), 8-methoxyflindersine ($\text{8c}$), N-methylflindersine ($\text{9a}$), zanthobunglanine ($\text{9c}$) oricine ($\text{9d}$) and veprisine ($\text{9e}$) and the prenylquinolone alkaloids atanine ($\text{13a}$), preskimmianine ($\text{13e}$) N-methylatanine ($\text{14a}$), O-methylglycosolone ($\text{14c}$) and N-methylpreskimmianine ($\text{14e}$) is described.     

Fluorocarbon derivatives of nitrogen. Part 11. Synthesis of some 2-(trifluoromethyl)imidazo[1,2-a]pyridines from trifluoroacetonitrile

3-(t-Butoxycarbonyl)-2-(trifluoromethyl)imidazo[1,2-$\text{a}$]-pyridine, prepared from trifluoroacetonitrile and pyridinium t-butoxycarbonylmethylide, reacts smoothly with trifluoroacetic acid to provide 2-(trifluoromethyl)imidazo[1,2-$\text{a}$]pyridine-3-carboxylic acid, which gives 2-(trifluoromethyl)imidazo[1,2-$\text{a}$]-pyridine when heated. 3-Cyano-2-(trifluoromethyl)imidazo[1,2-$\text{a}$]pyridine can be obtained $\text{via}$ treatment of trifluoroacetonitrile with pyridinium cyanomethylide, which is sufficiently reactive to effect nucleophilic displacement of fluorine from pentafluoropyridine under mild conditions [→pyridinium cyano(tetrafluoro-4-pyridyl)methylide].     

Intramolecular silyl migration in the singlet oxygenation of 2-methyl-5-trimethylsilylfuran

Tetraphenylporphyrin-sensitized photooxygenation of 2-methyl-5-trimethylsilylfuran ($\text{4}$) affords quantitatively trimethylsilyl 2-oxo-4-pentenoate ($\text{5}$), presumably via intramolecular Baeyer-Villiger rearrangement of the intermediary dioxirane ($\text{3a}$).     

Reaction between nucleoside base residues and the phosphorylating agent derived from 1-hydroxybenzotriazole and 2-chloroprenyl phosphorodichloridate

In the presence of 1-methylimidazole, 2-$\text{N}$-acyl guanine (as in $\text{4a}$), thymine (as in $\text{5a}$) and uracil (as in $\text{5b}$) residues react readily with the phosphorylating agent derived from 2-chlorophenyl phosphorodichloridate ($\text{1a}$) and 1-hydroxybenzotriazole.     

Ritter-reaction on steroids: Ring expansion of steroid oxethans into dihydrooxazines

The 3β-acetoxy-16β,17β-epoxymethyleneandrost-5-ene ($\text{1}$) transforms into the dihydrooxazine condensed to the sterane skeleton ($\text{4}$$\text{a}$,$\text{b}$,$\text{c}$,$\text{e}$,$\text{g}$,$\text{i}$) in a ring-expansion reaction with alkyl and aryl nitriles in the presence of HBF₄— diethyletherate The 3β-acetoxy-16α, 17α-epoxymethyleneandrost-5-ene ($\text{9}$) undergoes a Wagner-Meerwein rearrangement under similar conditions.     

Synthesis of silyl-substituted vinylallenes

The coupling between the 5-chloro-3-en-1-ynes $\text{1a}$ - $\text{1e}$ and trimetylchlorosilane gives rise to the vinylallenes $\text{2a}$ - $\text{2e}$ substituted by a trimethylsilyl group on the allenic moiety.     

Adamantane rearrangement mechanisms. 1,2-trimethylenenorbornanes

Unexpected differences in the aluminium bromide-catalyzed rearrangement behaviour of 1,2-$\text{endo}$-trimethylenenorbornane ($\text{1}$) and its 1,2-$\text{exo}$-isomer ($\text{2}$) are interpreted. Isotopic labelling studies indicate that reversible abstraction of the tertiary 2-$\text{endo}$ hydride in $\text{2}$ does not occur. Instead, rearrangement to $\text{6}$ is favored. The label scrambling in the final product, adamantane ($\text{8}$), is attributed to degenerate isomerization in the proto-adamantyl precursor, $\text{7}$.     

Facile syntheses of 2,4,6-cycloheptatrienyl ketones

The synthesis of the 2,4,6-cycloheptatrienyl ketones $\text{1a}$–$\text{1e}$ by two alternative routes is reported: Route 1): The adducts $\text{3a–c}$ from the phenyl(trimethylsiloxy)-acetonitriles $\text{2a–c}$, known as “umpolung” reagents, and tropylium tetrafluoroborate are cleaved by triethylammonium fluoride to form the aromatic cycloheptatrienyl ketones $\text{1a}$–$\text{1c}$. Route 2): the phenyl, methyl, and cyclopropyl ketone ($\text{1a}$, $\text{1d}$, $\text{1e}$) are prepared by treatment of the acid chloride $\text{7}$ with the corresponding organomanganese iodides RMnI ($\text{8a}$, $\text{8d}$, $\text{8e}$). The Fe-catalyzed coupling reaction of the acid chloride $\text{7}$ with a Grignard reagent was also used for the preparation of ketone $\text{1b}$.     

Stereocontrolled synthesis of 7-hydroxy- and 7-acetoxy-PGI2: New stable PGI2 analogues

Stable analogues of PGI₂, 7-hydroxy- and 7-acetoxy-PGI₂, were synthesized from protected PGI₂ methyl ester $\text{1b}$via sulfoxides $\text{6a}$, $\text{6b}$ through stereocontrolled sulfoxide-sulfenate rearrangement.     

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 ($\text{25}$).     

The facile (<−50°C) formation of cis-bicyclo[6.1.0]nona-2,4,6-trienes from cyclonona-1,3,5,7-tetraenes: A symmetry - forbidden reaction

The formation of the $\text{cis}$-bicyclo [6.1.0] nona-2,4,6-trienes $\text{4a}$-$\text{c}$ is not due to the sequence $\text{1}$ → $\text{2}$ → $\text{4}$, which would involve the symmetry-forbidden reaction $\text{2}$ → $\text{4}$ even at ?50°C. Rather, reaction of RX at C^4–7 of $\text{5}$, which is formed together with $\text{1}$, leads (probably via $\text{6a}$-$\text{c}$ and $\text{7a}$-$\text{c}$ to $\text{4a}$-$\text{c}$.     

Stereochemical studies — 79 synthesis and kinetic study on the retrodiene decomposition of norbornene-condensed 1,3-oxazin-4-ones

The $\text{cis}$-$\text{cxo}$- amino acid $\text{c}$ with norbornene skeleton was converted into 2-aryvl-$\text{cis}$-$\text{cxo}$-1,3-oxazin-4-ones $\text{5a}$-$\text{d}$. These compounds, similarly to the $\text{diendo}$ isomers $\text{1a}$-$\text{d}$ studied by us earlier, undergo retrodiene decomposition under mild conditions to give 2-aryl-6$\text{2}$-l,3-oxazin-6-ones ($\text{2}$$\text{a}$-$\text{d}$) in 50-60% yield. The ratio of the decomposition rate constants of the tricyclic $\text{diendo}$ and $\text{diexo}$-1,3-oxazin-4-ones, measured in toluene solution, is about 2.