[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.     

Methylated multibridged [2n]cyclophanes. All alternate synthesis of [26](1,2,3,4,5,6) cyclophane (superphane)

A sequence of formylation followed by a carbene insertion reaction has led to the stepwise introduction of additional ethano bridges into 4,5,7,8- tetramethyl [2₂](1,4)cyclophane ($\text{1}$), providing syntheses of 5,7,8-trimethyl- [2₃](l,2,4)cyclophane ($\text{6}$), a mixture of 5,8-dimethyl[2₄(1,2,4,5)cyclophane ($\text{10}$) and 5,7-dimethyl[2₄(1,2,3,5)cyclophane ($\text{11}$, and-4-methyl[2₅](1,2,3,4,5)-cyclophane ($\text{14}$). This route to $\text{14}$ completes a formal eight-step synthesis of [2₆](1,2,3,4,5,6)cyclophane ($\text{15}$, superphane) with an overall yield of 17%. A Birch reduction of $\text{6}$ readily gave 12,15-dihydro-5,7,8-trimethyl[2₃](1,2,4)-cyclophane ($\text{7}$) in 85% yield.     

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.     

Preferential formation of 8-epi-prostaglandin f2α via the corresponding endoperoxide by a biomimetic cyclization

Homolytic demercuration of the 1,2-dioxolanes 14a and 14b in the presence of oxygen leads preferentially to endoperoxidee 17 (both epimers at C*) which upon reduction affords 8-$\text{epi}$-prostaglandin F_2α and the C(15)-epimer, a result in accord with a previous mechanistic proposal.     

1,2-Dialkoxycarbonylhydrazine derivatives of pyrroles and indolizines. A new synthesis of cycl[3.2.2]azines

The reaction of pyrroles $\text{1}$ with diisopropyl azodicarboxylate $\text{2}$ yields 2- and 2,5-substituted derivatives. 3- and 1,3-substituted indolizines $\text{5}$ and $\text{6}$ are formed by the same route. Cycl[3.2.2]azines $\text{7}$ have been obtained from $\text{5}$ and $\text{6}$ with dimethyl acetylenedicarboxylate.     

Thermolysis of [1,2,4]triazolo[1,5-a]pyrimidine n-ylides

5,7-Dimethyl[1,2,4]triazolo[1,5-a]pyrimidinio-3-phenacylide ($\text{3}$) generated by the reaction of an iminium salt ($\text{2}$) with 1 eq. of triethylamine, underwent a new thermal ring cleavage of the triazole moiety to give the pyrimidine derivative. However reaction of $\text{2}$ with 2 eq. of triethylamine afforded the 2-iminooxazoline derivative. The iminooxazoline reacted with nucleophiles such as alcohols or amines to give imidazoles.     

Enamine chemistry-XXVI: The [4 + 2] cycloaddition reactions of 3-amino-1-(4-nitrophenyl)-prop-2-ene-1-thione with electrophilic olefins and acetylenes

Enamino-thiones 1 prepared from the corresponding enaminones by thiation with Lawesson's Reagent, were allowed to react with 2-chloroacrylonitrile and dimethyl acetylenedicarboxylate giving dihydro-2$\text{H}$-thiopyrans, 2, and 4$\text{H}$-thipyrans, 3, respectively. The reaction of 1a with ethyl propiolate at room temperature afforded 4$\text{H}$-thipyrans, 4a, which on standing rearranged to 2$\text{H}$-thiopyran, 5a(1, 3 amide shift). The reaction of 1b with ethyl propiolate produced 4b and 5b. Some of the ¹³C NMR data are reported.     

A pios study of the reaction Ne(3P2,0) + HCl → Ne + HCl+ (A2Σ+) + e−

The HCl⁺ (A) vibrational state distributions from the title reaction were studied over the 48–110 meV collision energy range. The $\text{1}\text{0}$ and $\text{2}\text{0}$ ratios increase by factors of about 1.3 and 2.5, respectively. The branching ratios appear to be determined primarily by Franck-Condon factors, and by the endoergicity of the ν′ = 2 level.     

[4+2]cycloaddition reactions of triarylphosphaalkene

Cycloaddition reactions of mesityl(diphenyliiifithylene)phosphine ($\text{1}$) were Investigated. With several dienes, no Diels-Alder reactions were oEserved. With azides, diphenyidiazomethane and 2,4,6-trimethylbenzonitrile oxide, the corresponding cycloadducts ($\text{4}$$\text{12}$$\text{17}$$\text{12}$were obtained. In the case of phenyl azide, a competing Staudinger reaction occurred leading to $\text{3}$.     

Terpenes and terpene derivatives - XV. [1 ] Synthesis of 4,8-dimethyl-2-(2-methyl-1-propenyl)--1-oxaspiro(4.5]dec-7-ene (“bisabolene oxide”)

Starting from the ketones $\text{3}$ and $\text{4}$ the synthesis of six spiro ethers with an l-oxaspiro[4.5]decane skeleton is described. Five of them, $\text{9a}$,$\text{b}$, $\text{10a}$,$\text{19}$ and $\text{19}$ represent typical partial structures of the sesquiterpenoid spiro ether $\text{1}$. The unambiguous synthesis of $\text{1}$ shows a previous assignment of “'bisabolene oxide“' to structure $\text{1}$ to be wrong.     

v-Triazolines. part XXI. Spiro[bicyclo[2.2.1]hept-2-ene[54']1',2'.s'-triazole]derivatives from cyclopentadiene and 5-amino-4-methylene-v-triazolines

1R^*, 4R^*, 5S^*, 5'S^*-5'-Amino-1'-(4-nitrophenyl)-4',5'-dihydrospiro[bicyclo [2.2. 1]hept-2-ene[5.4]-1',2',3'-triazoles]$\text{2}$ have been obtained both by ?4 +2]-cycloaddition of cyclopentadiene to amino-methylene-1-(4-nitrophenyl)-4,5-dihydro-v-triazoles $\text{1}$ and by [3+2]-cycloaddition of 4-nitrophenylazide to 5-aminomethylene-2-norborenes $\text{4}$. The configuration has been fully established by X-ray crystallographic analysis. The course of the cycloaddition and the thermal behaviour of $\text{2}$ are discussed.     

Synthesis applications of aza-cope rearrangements.: Stereocontrolled synthesis of cyclohepta [b]pyroolidines1

Both $\text{cis}$- and $\text{trans}$-3a-aryl-4-oxo-decahydrocyclohepta[b]pyrroles can be prepared in stereocontrolled fashions by the reaction of 2-amino-1-(1-phenyl- vinyl)cyclohexanols with formaldehyde and acid.     

Addition von organomagnesium-verbindungen an nicht aktivierte CC-doppelbindungen: III. 2-alkenylmagnesiumhalogenide und bicyclo[2.2.1]hept-2-en

2-Methyl-2-propenyl- (I) and 2-Butenylmagnesium halide (II) react with bicyclo[2.2.1]hept-2-en (III) erhaltenen $\text{1}\text{1}$-Addukte (IV) und (V) lagern sich converted by heating under opening of one 5-ring. On the basis of the products of hydrolysis, the dialkenylcyclopentanes (X) and (XI), formed by conversion of (V), the mechanism of this reaction hitherto unknown for a saturated 5-cyclic compound is discussed.     

The [4.4.4.4]Fenestranes and[2.2.2.2]paddlane. Prospects for the realization of planar tetracoordinate carbon?

Semi-empirical (MINDO/3 and UNDO) MO calculations on highly strained planar tetracoordinate carbon candidates indicate the central carbons in $\text{cis}$- [4.4.4.4] fenestrane ($\text{1}$) to have pyramidal ($\text{1a}$) and in trans-[4.4.4.]fenestrane ($\text{2}$) to have distorted tetrahedral ($\text{2a}$) geometries. In [2.2.2.2]paddlane ($\text{3}$), the two central carbons are pentacoordinate. Each is nearly coplanar with four carbon neighbours; additionally, the two bridgehead carbons are connected by a single bond ($\text{3a}$).     

Transition structures for the reaction of difluorocarbene with propene

Two $\text{ab}$$\text{initio}$ transition structures for the reaction of difluorocarbene with propene have been located with gradient techniques and the 3-21G basis set. The activation energy is 1.3 kcal/mol lower than for the reaction with ethylene. Two transition structures with the fluorines approaching $\text{syn}$ or $\text{anti}$ to the methyl group are identical in energy     

Functionalized 2-azabicyclo[3.3.1]nonanes. III.1 reductive rearrangement of an hexahydro-2-oxopyrano[3,2-b]pyridine

Reduction of 5-benzoyl-8-methyl-2-oxo-3,4,4a,5,6,7-hexahydro-2H-pyrano[3,2-b] pyridine ($\text{1}$) with lithium aluminium hydride afforded (1R^*,5S^*,6R^*,9S^*)-2-benzyl-5-methyl-2-azabicyclo[3.3.1]nonane-6,9-diol ($\text{2}$).     

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.     

Nitrogen bridgehead compounds part 16. Facile total synthesis of 7,8-dihydro-13H-indolo[2′,3′:3,4]pyrido[2,1-b]quinazolin-5-one (Rutecarpine).

Rutecarpine $\text{1}$ has been synthetised from hydrazone $\text{2}$, in high yield by Fischer indole synthesis, Hydrazone $\text{2}$ has been prepared from $\text{3}$ with benzenediazonium chloride or $\text{5}$ with phenylhydrazine. $\text{2}$ Shows a solvent dependent E-Z isomerism.     

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, $\text{3a}$-$\text{3c}$.