Stereospecific deoxygenation of 1,2-diols to olefins

The 2-dimethylamino-1,3-dioxolane derivatives of 1,2-diols when treated with trifluoromethane sulfonic anhydride and diisopropylethylamine in toluene give the corresponding olefins stereospecifically under mild experimental conditions.     

Reaction of amino radicals with olefins: Theoretical aspects

The role of photocatalysts in improving the photochemical synthesis of fatty amines has been examined. Ab initio SCF and CI calculations for the addition of the aminyl radical NH₂^• to ethylene are reported. In contrast with previous theoretical results a low activation energy and a rather small exothermicity were determined. Thus an explanation for the known inactivity of amino radicals in addition reactions can be found in the possibility of a retroaddition. The calculations indicate that the role of photocatalysts could be explained by a significant stabilization of the addition photoproduct blocking the reversibility of the process. The involvement of the photocatalyst with the primary photoproduct NH₂^• should also be considered in view of a significant increase in the exothermicity observed.     

Reaction of adamantane series olefins with N-bromosuccinimide

Features of allyl bromination of sterically hindered adamantane series olefins with N-bromosuccinimide were investigated. A series of unsaturated mono- and polybromo adamantane derivatives was synthesized. The configuration of compounds obtained was established using 2D NOESY NMR spectroscopy.     

Reaction of mercaptopyrimidine derivatives with perfluoro olefins

The reaction of methyl and hydroxy derivatives of 2- and 4-mercaptopyrimidines with perfluoropropylene and perfluoro-1-hexene was investigated. The corresponding perfluoroalkenylthio-substituted pyrimidines are described.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 402–406, March, 1984.     

Reaction of benzyne with cyclic olefins—II : Ene addition to some cycloalkenes

Addition of benzyne to 1-methylcyclohexene, (+)-carvomenthene, (+)-limonene, α- and β-pinenes and δ³-carene has been investigated. Structures to the ene products formed are assigned on the basis of spectroscopic evidence. Arguments are advanced in favour of a concerted ene mechanism for the addition of benzyne to these olefins.     

Reaction of vinylcarbenoids with benzaldehydes: formation of vinylcarbonyl ylides followed by ring closure to oxiranes and dihydrofurans

Rh(2)(OAc)(4)-catalyzed reaction of vinyldiazo compound 1a in the presence of p-methoxybenz- 2a, mesit- 2b, and p-chlorobenzaldehyde 2c gave a mixture of isomeric vinyloxiranes 3a-c and 4a-c, and sterically unstable (E)-dihydrofurans 5a-c, but not stable (Z)-dihydrofurans 6. However, the reactions with p-nitro- 2d and 2,4-dinitrobenzaldehyde 2e gave (Z)-dihydrofurans 6d,e along with 3d, 4d, and 5d,e. The reaction in the presence of maleic anhydride and dimethyl fumarate gave single 1,3-dipolar cycloadducts 11 and 13, respectively, indicating that a single conformer, the sterically unstable endo-aryl-endo-cyanostyryl carbonyl ylide 14 (15), is initially formed in the reaction of 1 with 2. It was concluded that the endo-vinyl-exo-aryl vinylcarbonyl ylides 17a-c arising from 2a-c undergo disrotatory cylization to exclusively produce 5, whereas the ylides 17d,e arising from 2d,e undergo partly symmetry-forbidden conrotaory cyclization to sterically stable trans-diaryldihydrofurans 6d,e as well as the symmetry-allowed process to 5d,e.     

Reaction of trimethylsilyl azide with bridged bicyclic olefins

Bridged bicyclic olefins were found to undergo facile 1,3-cycloaddition reaction with trimethylsilyl azide. Norbornene produced cis,exo-1-trimethylsilyl-4,7-methano-3a,4,5,6,7,7a-hexahydrobenzotriazole, while norbornadiene formed a diadduct with cis,exo-stereochemistry, together with 2-trimethylsilyl-1,2,3-triazole produced by a retro-Diels—Alder reaction of an intermediate mono-adduct. Dicyclopentadiene reacted only at the norbornene position while α-pinene did not react with trimethylsilyl azide. In contrast to aryl- and sulfonyl-azide adducts of norbornene derivatives, which decompose upon heating the present adducts were recovered unchanged after prolonged treatment at 205°C.     

Reaction of thiolsulfinates with trihaloacetic anhydrides. II : Addition of sulfenyl trihaloacetates to olefins

Treatment of thiolsulfinates with trifluoro- or trichloroacetic anhydride at -20°C in the presence of various olefins in carbon tetrachloride afforded the corresponding β-trifluoro- or trichloroacetoxy sulfides in good yields. The β-trihaloacetoxy sulfides are considered to be resulted by the electrophilic addition of the sulfenyl trihaloacetates, formed as transient intermediates, to olefins. The addition takes place stereospecifically in $\text{trans}$ manner and the regioselectivity for the addition with unsymmetrical olefins obeyed the Markownikoff orientation rule, except 3,3-dimethyl-1-butene which gave initially the anti-Markownikoff product $\text{3}$ due to the steric hindrance, however the adduct $\text{3}$ is readily converted to the Markownikoff product $\text{22}$ upon heating. Since the addition is highly regioselective and stereospecific, this is a very convenient procedure for the syntheses of β-trihalo-acetoxy sulfides.     

The reaction of lithium trialkylalkynylborates with oxiranes : γ-Hydroxyketone synthesis and stereoselective preparation of trisubstituted ethylenes

Lithium trialkylalkynylborates (1) react with oxiranes (2) to give non-isolable intermediates 3 which subsequently afford either γ-hydroxyketones 5, trisubstituted ethylenes of homoallylic alcohol type 6 or a tetrasubstituted ethylene 7 upon appropriate treatment with NaOH/H₂O₂, AcOH or NaOH/I₂, respectively. The reaction of oxiranes with 1 proceeds in high regioselectivity and the resulting homoallylic alcohols 6 are of nearly 100% (E) configuration. A straight chain γ-hydroxyketone 16 is obtained in the reaction of methyloxirane with the ate-complex (1), which has been prepared from lithium acetylide ethylenediamine complex and trihexylborane.