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.     

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 $\text{4a}$-$\text{c}$.     

A synthetic approach to crown ether analogs by the remote photocyclization with a pai system of phthalimide and methylthio groups

Upon irradiation a homologous series of certain phthalimides ($\text{2a}$-$\text{c}$) possessing a terminal sulfide function in their N-poly-ether side chain undergo regioselective remote photocyclization affording seven to fifteen-membered crown ether analogs ($\text{3a}$-$\text{c}$) in moderate yields.     

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.     

Studies on nucleosides and nucleotides. X. desulfurization of 2′,3′-0-Isopropylidene-2-thiouridines by dibenzoyldiazene

The reaction of dibenzoyldiazene with 2′,3′-0-isopropylidene derivatives of 2-thioridine, 5-methyl-2-thiouridine, and 5-methoxycarbonylmethyl-2-thio-uridine afforded the corresponding desulfurized products, $\text{3a}$-$\text{3c}$.     

Base catalysed rearrangement of 2-methyl-3,3-bisalkylthioacrylophenones to 2-alkylthiomethyl-3-alkylthioacrylophenones via mobile keto allyl intermediates

The title compounds ($\text{1a}$-$\text{e}$) undergo facile base catalysed rearrangement to give $\text{5a}$-$\text{e}$. A mechanism involving thioallylic rearrangement of intermediates, 2-bisalkylthiomethyl acrylophenones, ($\text{3a}$-$\text{e}$) has been proposed.     

Biomimetic synthesis of bacterial c50 carotenoids decaprenoxanthin and c.p. 450

Alkylation of the distal double bond of pseudoionone $\text{4}$ has been carried out with isoprene epoxide (ZnCl₂ /MeNO₂ ) leading directly to α-$\text{cis 10 a}$, α-$\text{trans}$$\text{10b}$ and γ $\text{10c}$ hydroxyprenylionones. The α-$\text{cis}$ and γ-isomers have been converted in few steps into the C₅₀ carotenoids decaprenoxanthin $\text{1}$ and C.p. 450 $\text{3}$ respectively.     

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 $\text{1b}$.     

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.     

Nucleosides, 45.-Assignment of glycosylation sites in o-hexopyranosyl-ribonucleosides by 13C-NMR

Evidence is presented that glycosylation of a ribose-OH group in nucleosides results in a significant downfield shift for the appended ¹³C nucleus and smaller upfield displacements for the adjacent carbons, providing an efficient tool for differentiating between 2′-$\text{o}$-, 3′-$\text{o}$- and 5′-$\text{o}$-glycosyl-ribonucleosides. Therewith, the products formed on enzymatic galactosylation of uridine, inosine, and adenosine are unequivocally assigned β(1→3)-glycosidic linkages ($\text{3a}$ – $\text{3c}$).     

Synthesis and crystal structure of 1,1,1,5,5,5-hexafluoro-2-aminopentan-4-one (HFAP)

The vapour phase reaction of ammonia and hexafluoroacetylacetone leads to the formation of the new β-keto-amine C₅H₃F₆NO. Crystals of the compound are monoclinic, space group $\text{P}$2₁/$\text{n}$, $\text{a}$ = 10.01(2), $\text{b}$ = 19.33(3), $\text{c}$ = 8.40(1) Å, β = 82.27(6)°; final R = 0.044.     

New SbS2 strings in the BaSb2S4 structure

The new compound BaSb₂S₄ crystallizes in the monoclinic system (space group: $\text{P2}{}_1\text{c}$, No. 14) with a = 8.985(2) Å, b = 8.203(3) Å, c = 20.602(5) Å, β = 101.36(3)°. SbS₃ ψ tetrahedra and ψ-trigonal SbS₄ bipyramids are connected by common corners and edgers to infinite strings. These are arraged cross-wise in sheets perpendicular to the c axis.     

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.     

Synthesis of enantiomerically enriched atrolactic acid and other α-hydroxy acids

The α-anions of 2-substituted 1,3-dioxolan-4-ones derived from chiral mandelic and lactic acid ($\text{2a}$, $\text{2b}$; $\text{3a}$; $\text{10a}$, $\text{10b}$) were alkylated with high stereoselectivity. The products formed were hydrolysed to α-hydroxy acids with 65–85% e.e. ((S)(+)-$\text{5}$,$\text{7}$,$\text{9}$, (R)(–)-$\text{13}$).     

A nitrosamine route to (±)-macrostomine

In a synthetic approach to macrostomine $\text{1}$, both side chains of the isoquinoline nucleus are attached by high yield carbon carbon bond formation with lithiated nitrosamines ($\text{2b}$ → $\text{3a}$, $\text{3c}$ → $\text{4a}$).     

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].     

The syntheses of polycyclic molecules containing b-carboline units by the photochemically induced ring closure of enamides

The syntheses of 5-methyl-5,8,9,14-tetrahydroindolo(2,3-$\text{c}$)indolo (2,3-$\text{g}$) quinolizin-6-one and 15-methyl-7,8,13,15-tetrahydroindolo ( 3,2-$\text{c}$) indolo(2,3-$\text{g}$)quinolizin-5-one from the photochemical cyclisation of i-methylene-2-(N-`methylindole-2'-carbonyl) 1,2,3,4-tetrahydro-B-carboline and 1-methylene-2- (N-`methylindole-3' carbonyl) 1,2,3,4,-tetrahydro-B-carboline are described. Attempts to prepare indolo(2,3-$\text{c}$)isoquinolines from the photochemical cyclisation of 2-benzamidoindoles were unsuccessful.     

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.     

6-alkyl- and 5,6-dialkyl-2-methoxy-4(3H)-pyrimidinones in the transformations of pyrimidines. Regiospecific 1-N-acylation of pyrimidines.

Transformation of 6- and 5,6-dialkyl-2-methoxy-4(3H)-pyrimidinones (1a and 1b) into 1-$\text{N}$-acylated-pyrimidine derivatives 3($\text{a}$-$\text{f}$) under Friedel-Craft like conditions is presented. In different acylation conditions 4-O-acylated-pyrimidines (5a and 5b) are also obtained. Compounds (3c) and (3f) can be directly converted into 1-$\text{N}$-acyl-protected-isouridine analogues (8a and 8b).     

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.