Transition-metal-catalyzed addition of heteroatom-hydrogen bonds to alkynes.

The preparation, structure, and chemistry of hypervalent iodine compounds are reviewed with emphasis on their synthetic application. Compounds of iodine possess reactivity similar to that of transition metals, but have the advantage of environmental sustainability and efficient utilization of natural resources. These compounds are widely used in organic synthesis as selective oxidants and environmentally friendly reagents. Synthetic uses of hypervalent iodine reagents in halogenation reactions, various oxidations, rearrangements, aminations, C–C bond-forming reactions, and transition metal-catalyzed reactions are summarized and discussed. Recent discovery of hypervalent catalytic systems and recyclable reagents, and the development of new enantioselective reactions using chiral hypervalent iodine compounds represent a particularly important achievement in the field of hypervalent iodine chemistry. One of the goals of this Review is to attract the attention of the scientific community as to the benefits of...

Advances in Synthetic Applications of Hypervalent Iodine Compounds

Lewis Acids: From Conventional Homogeneous to Green Homogeneous and Heterogeneous Catalysis

Kraitchman has shown that a single isotopic substitution on an atom is sufficient to determine directly the coordinates of that atom with respect to the principal axes of the original molecule. Kraitchman's formulas represent exact solutions of the equations for the equilibrium moments of inertia. However, the effects of the zero‐point vibrations are such that the coordinates obtained by substitution from the ground state moments of inertia I0 are systematically less than r0. These coordinates have here been called r (substitution) or rs, and it is found that rs≃(r0+re)/2, and Is= ∑ imirsi2≃(I0+Ie)/2.In the usual method of solution, the coordinate of one atom is determined from the equation for I0, and therefore the difference I0—Is must be made up by this one coordinate. This introduces a large error in the structures normally determined from ground state constants, and results in variations of 0.01 A in structures determined from different sets of isotopic species. If instead, we obtain the structure on...

A new criterion for the determination of molecular structures from ground state rotational constants

Additions of Organometallic Reagents to C=N Bonds: Reactivity and Selectivity

The reaction of epoxysilanes with lithiated allylsilanes gives predominantly α-silyl-substituted alcohols(3) which are convenient precursors for the preparation of 1-silyl-substituted 1,4-dienes.

Regiospecific synthesis of 1-silyl substituted 1,4-dienes

The unimolecular gas-phase thermolytic decomposition of 1,1,3,3-tetramethyl-2-thiocarbonylcyclohexane S-oxide (3) has been studied as a function of temperature by a flash vacuum thermolysis (f.v.t.) technique. The products detected are the carbenes (4) and (5), the ketone (6), the keten (7), the thioketone (8), and the thioketen (9). The product ratio is highly dependent on the thermolysis temperature. The thermolysis of (3) is mechanistically rationalized by assuming the existence of only two concurrent primary processes, which are (a) extrusion of atomic oxygen, leading to the thioketen (9), and (b) electrocyclic ring closure into the corresponding three-membered oxathiiran (10). The latter is dominant at lower temperatures, whereas higher thermolysis temperatures favour atomic oxygen extrusion. At further elevated temperatures additional concurrent primary reactions, i.e. extrusions of SO and CSO leading to the carbenes (5) and (4), respectively, are observed. Owing to an apparently very short half-life of the oxathiiran (10), only the decomposition products of the three-membered ring compound have been detected. These are the thioketone (8), formed by rearrangement of (10) into the α-thiololactone (11) followed by loss of CO, minor amounts of the ketone (6), formed analogously, and the keten (7), as a result of simple sulphur extrusion.

Gas-phase thermolysis of a thioketen-S-oxide

The Unusual Stereochemistry of the Cycloaddition of Vinyl Ethers with Sulfonyl Isothiocyanates

Starting from (R)-O-benzylglycidol and a sulfur-stabilized allyl anion, a (3 + 3) synthesis of the α,β-unsaturated (6S)-δ-lactone 7 is achieved. Subsequent diastereoselective addition of a phenyldimethylsilyl cuprate and unmasking of the latent hydroxy function provides the lactone unit of compactin.

Ernst Schaumann

Papers

Regiospecific synthesis of 1-silyl substituted 1,4-dienes

Gas-phase thermolysis of a thioketen-S-oxide

The Unusual Stereochemistry of the Cycloaddition of Vinyl Ethers with Sulfonyl Isothiocyanates

A Facile Asymmetric Synthesis of the Compactin Lactone Moiety

Lewis acid supported reactions of 1,3-bis(silyl)allyl compounds with epoxides — inter- and intramolecular versions