Reaction of 3-azido-5-phenyl-1,2,4-oxadiazole with dimethylformamide,a new deoxygenative coupling reaction

When 3-bromo-5-phenyl-1,2,4-oxadiazole (1b) is heated with sodium azide in anhydrous dimethylformamide at 130°, 3-dimethylamino-($\text{1c}$) and 3-dimethylaminomethyleneamino-5-phenyl-1,2,4-oxadiazole ($\text{1d}$) are formed, the latter by a new deoxygenative coupling of the azide ($\text{1a}$), or the nitrene derived from it, with the solvent.     

[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 $\text{3}$.     

Heterocyclic and acyclic derivatives of F-N-isopropylacetimidoyl chloride

$\text{F}$-N-Isopropylacetimidoyl chloride, CF₃CClNCF(CF₃)₂, has been used as a precursor for a variety of heterocyclic and acyclic compounds. Reaction with azide ion yields a mixture of the imidoyl azide, CF₃(N₃)CNCF(CF₃)₂, and the 1,5-tetrazole, CF₃$\text{CNNN}$CF(CF₃)₂. Hexafluoropropylideniminolithium produces as a minor product the conjugated diimine, (CF₃)₂CNC(CF₃)NCF(CF₃)₂, from nucleophilic attack at the imidoyl chlorine and as a major product the triimine, (CF₃)₂CNC(CF₃)NC(CF₃)₂NC(CF₃)₂, from further attack at the isopropyl fluorine. A thio-amide, CF₃C(S)NHCH(CF₃)₂, and a Δ³-1,2,4-dithiazoline, $\text{SSC(CF}{}_3\text{)NC}$(CF₃)₂, are produced upon reaction of hyrogen sulfide with the imidoyl chloride. Pathways are proposed for each of the reactions.     

Intramolecular [4 + 1] pyrroline annulation approach to pyrrolizidine alkaloids. Formal total synthesis of (±)-supinidine.

Dienic azide $\text{7}$ was found to yield dehydropyrrolizidines $\text{10}$ and $\text{11}$ on thermolysis. The synthesis of these compounds is described and the mechanistic implications as well as synthetic utility of this new annulation sequence is discussed.     

The reaction of vinyl azides with sulfoxonium ylids. Synthesis of n-vinyl triazolines and vinyl aziridines.

Vinyl azides $\text{1}$ react with dimethylsulfoxonium ylid $\text{3}$ at the azide function to produce in high yield 1-vinyl-4,5-unsubstituted-Δ-1,²-1,2,3-triazolines $\text{4}$. Vacuum flash pyrolysis of $\text{4}$ furnished N-vinylaziridines $\text{7}$ without formation of pyrolines.     

A novel synthesis of 3-cyanoindoles and a new route to indole-3-carboxylic acid derivatives

2-Alkyl-3-cyanoindoles are obtained when 1-alkylmethyl-2-chloro-(or 2-phenylsulfonyl)-3-phenylsulfonylindoles are reacted with excess azide ion (90°/DMF). The reaction is considered to occur by a fragmentation recombination process in which the Schiff's base $\text{12}$ is of central importance. This proposal is supported by the formation of 2-substituted indole-3-carboxylates $\text{17}$ from aldehydes and the α-phenylsulfonyl-$\text{o}$-aminophenylacetic acid ester derivative $\text{16}$.     

Nitrogen bridgehead compounds. Part 60. Unusual amination with sodium azide.

9-Bromo-6,7,8,9-tetrahydro-4$\text{H}$-pyrido [1,2-$\text{a}$]pyrimidin-4-ones react with sodium azide to afford 9-amino-6,7-dihydroanalogues. A mechanism involving a tricyclic tetrazine intermediate formed by neighbouring-group participation is suggested.     

Aromatisierung von cytclohexenon-derivaten über selenorganische zwischenstufen

Reaction of the hydroaromatic compounds ($\text{1a}$) and ($\text{3a}$) with lithium-diisopropylamide followed by phenylselenenyl chloride gives the selenides ($\text{1b}$) and ($\text{1c}$) resp. ($\text{3b}$), which form exclusively the phenols ($\text{4}$) resp. ($\text{6}$) after oxidation with 3-chloroperbenzoic acid in the presence of 3,5-dimethoxyaniline ($\text{7a}$).     

Stereoselektive synthese von α-glucosiden mit 1,1′ -diacetal-struktur

Reaction of ($\text{1b}$) and ($\text{1d}$) with the acetal ($\text{2a}$) in presence of trimethylsilyl trifluoromethanesulfonate at ?70° C gives the α-glucosides ($\text{3a}$) and ($\text{4a}$), whereas ($\text{1a}$) and ($\text{1c}$) lead to the β-glucosides ($\text{4c}$) and ($\text{4b}$). At 0° C reaction of ($\text{1a}$) with the acetals ($\text{2b-g}$) gives exclusively the α-glucosides ($\text{3b-g}$).     

Diels-alder reactions of malondialdehyde derivatives with reversed electron demand; an easy approach to structurally unique carbohydrates and compounds of the thromboxane type

2-Formyl-malondialdehyde ($\text{1}$) reacts at 22°C in a type of Diels-Alder reaction with reversed electron demand with the enol-ethers ($\text{18}$) – ($\text{21}$) and ($\text{23}$) – ($\text{25}$) within a frew hours to give the dihydropyrans ($\text{2}$) – ($\text{9}$) and ($\text{12}$) – ($\text{17}$). Thio-enol-ethers may also be employed in this cycloaddition.     

Nachbargruppenbeteiligungen bei der substitution von 2-amino-2-desoxy-α-d-glucopyranosiden in der 3-stellung

Neighboring group participation severely restricted nucleophilic substitution of N-protected 2-amino-2-deoxy-3-O-mesyl-α-D-glucopyranosides with azide ion. N-acetyl as blocking group led to the formation of the oxazoline $\text{3}$ while from N-dinitrophenylderivatives epimers were formed via the aziridine $\text{11}$.     

Synthesis of oxazolidin-2-ones using carbonate ion on a polymeric support

Through the insertion of a carbon dioxide molecule, the oxazolidin-2-ones ($\text{5a}$) and ($\text{5b}$) were prepared by treataent of the salts ($\text{4a}$) and ($\text{4b}$) with carbonate anion on polymeric support. The hydrolysis under basic conditions of ($\text{5a}$) and ($\text{5b}$) afforded the erythro-3-amino-1,2-diols ($\text{6a}$) and ($\text{6b}$) which were fully acetylated: the 2-amino-2-deoxyerythritol derivative ($\text{7b}$) was obtained in 91% yield.     

The 185-nm photochemistry of 2,3-diazabicyclo[2.2.1]heptene and of its denitrogenation products bicyclo[2.1.0]pentane and cyclopentene

The 185-nm denitrogenation of 2,3-diazabicyclo[2.2.1]heptene ($\text{1}$) afforded bicyclo[2.1.0]-pentane ($\text{2}$) and cyclopentene ($\text{3}$) presumably via a “hot” cyclopentane-1,3-diyl diradical ($\text{8}$); 1,4-pentadiene ($\text{4}$) and methylenecyclobutane ($\text{5}$) were secondary products of the 185-nm photolysis of ($\text{2}$) and ($\text{3}$).     

Novel fluoride transfer in the reaction of tricyclic epoxides with boron trifluoride

Reaction of the tricyclic epoxides ($\text{1a}$) and ($\text{1b}$) with boron trifluoride etherate leads to fluorohydrins ($\text{2a}$) and ($\text{2b}$) derived in the novel fluoride transfer, whereas ($\text{1c}$) undergoes isomerization to spiro ketone ($\text{3}$).     

Synthesis of 3,3,3-trifluoropropionic and 4,4,4-trifluoro-2-ketobutyric acids

Trifluoroethyl cyclohexyl ketone ($\text{4}$) is prepared by acylation of difluoroethylene ($\text{2}$) with cyclohexanecarboxylic acid chloride ($\text{1}$), followed by Cl→F exchange with potassium fluoride in the presence of triethylbenzyl- ammonium chloride. Bayer-Villiger oxidation of ketone ($\text{4}$) with trifluoroperacetic acid gives cyclohexyl trifluoropropionate ($\text{5}$). 3,3,3-trifluoropropionic acid ($\text{6}$) is obtained by treatment of ($\text{5}$) with trimethylsilyl iodide. Condensation of 2,2,2-trifluorodiazoethane ($\text{7}$) with ethyl glyoxylate ($\text{8}$) gives mainly ethyl 4,4,4-trifluoro-2-ketobutyric acid ester ($\text{9}$) which leads after hydrolysis to the corresponding acid ($\text{12}$).     

Syntheses of enantiomeric dihydropyrans through stereocontrolled intramolecular cycloaddition

Reaction of the cyclic 1, 3-dicarboxylic acid derivatives ($\text{1}$), ($\text{2}$) and ($\text{3}$) with (R)- or (S)-citronellal ($\text{4}$/$\text{5}$) gives the enantiomeric tricyclic dihydropyrans ($\text{10}$), ($\text{11}$), ($\text{12}$) and ($\text{13}$), probably via a 100% stereocontrolled intramolecular cycloaddition.     

Photochemical studies. Irradiation induced transformations of 1,2-dihydrophthalides

The photochemical behavior of $\text{cis}$-1,2-dihydrophthalide ($\text{1}$) and its 1,2-trimethylene derivative ($\text{4}$) was studied. Besides bicyclo[2.2.0]hexene formation in both cases, ($\text{1}$) transforms into its $\text{trans}$ isomer ($\text{3}$) whereas ($\text{4}$) undergoes a 1,2-shift to ($\text{7}$).     

Completely stereoselective synthesis of all four stereoisomeric 1-carbamoyloxy-1,3-alkadienes via anti-diastereoselective homoaldol reaction from aldehydes and a single carbon-three-unit

Lithiation of both ($\text{Z}$)- and ($\text{E}$)-3-trimethylsilyl-2-propenyl $\text{N}$,$\text{N}$-diisopropyl carbamate 2 affords the (2$\text{E}$) -lithium compound 3. Aluminium- or titanium-mediated addition to aldehydes, 4 gives (1$\text{E}$)-(3$\text{R}$*4$\text{S}$*)-enol carbamates 7. A stereospecific Peterson elimination (borontriflouride- or base-mediated) introduces the second double bond either with (3$\text{E}$)- or with (3$\text{Z}$)-configuration. So just by reagent selection for each of the two steps, (1$\text{E}$,3$\text{E}$)-, (1$\text{E}$,3$\text{Z}$)-, (1$\text{Z}$,3$\text{E}$)-, or (1$\text{Z}$,3$\text{Z}$)- dienes 8 - 11, respectively, are prepared with stereoselectivities up to > 99.7%     

On the question of carbonyl oxide intermediates in the oxygen transfer by furan endoperoxides and bicyclic ozonides: intramolecular trapping experiments

On heating the furan endoperoxide ($\text{2}$) rearranges into the enol ester ($\text{4}$) and the bicyclic ozonide ($\text{3}$) affords instead the rearranged ozonide ($\text{7}$). The process ($\text{2}$) → ($\text{4}$) represents an intramolecular Baeyer-Villiger rearrangement presumably via the dioxirane (D-2), while the process ($\text{3}$) → ($\text{7}$) represents intramolecular trapping of the carbonyl oxide (C-3).     

Synthesis of 2-isopropylfuro(2,3-b)quinolines-a new synthesis of (±)-lunacrine, (±)-lunasine and (±)-demethoxylunacrine

A new and convenient synthesis of 2-isopropylfuro-(2,3-b)quinolines ($\text{4}$) from 3-(3-methylbut-1-enyl)-2-quinolones ($\text{2}$) is described. A neat synthesis of the alkaloids (±)-lunacrine ($\text{1a}$), (±)-lunasine ($\text{12a}$) and (±)-demethoxylunacrine ($\text{1b}$) is also reported.