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

Reaction of dialkylthioketenes with tetracyanoethylene oxide yields dicyanomethylenethiiranes in a sequence involving [3 + 2] cycloaddition, cycloreversion and rearrangement. In contrast, a thioketene with a sulfide moiety reacts preferentially on the latter to give the stable sulfur ylide 9.

Dicyanomethylenethiiranes from Thioketenes and Tetracyanoethylene Oxide.

Easily available 1,3-bis(silyl)allyl compounds react with epoxides under Lewis acid catalysis to give interesting synthetic building blocks. The course of reaction depends on the stabilization of cationic intermediates by the silicon β-effect.

Lewis Acid Supported Reactions of 1,3‐Bis(silyl)allyl Compounds with Epoxides — Inter‐ and Intramolecular Versions.

Synthesis of 1‐Functionalized Silylcyclopropanes via Cyclization of 3‐Silylalk‐4‐enols.

Cycloadditionsreaktionen von heterokumulenen 3. mitt. thermische cycloadditionsreaktionen von heterokumulenen mit 2-dialkylaminoazirinen

At low temperature, sulfonyl isocyanates 1 react with ketene O,N-acetals 2 to give 1,4-dipoles 3. On warming, dipoles 3 rearrange in a formal ON methyl sift to give malonamides 4. A crossover experiment starting from 2a and 2b with a deuterated O-methyl group gave scrambling of the label and thus confirmed the intermolecular nature of the methyl transfer.



Bei niedriger Temperatur reagieren Sulfonylisocyanate 1 und Keten-O,N-acetale 2 zu 1,4-Dipolen 3. Beim Erwarmen lagern sich die Dipole 3 in einer formalen ON-Methyl-Wanderung zu Malonamiden 4 um. Ausgehend von 2a und 2b mit deuterierter O-Methyl-Gruppe gab ein Kreuzungsversuch halbdeuterierte Produkte und bewies so, das die Methyl-Verschiebung intermolekular verlauft.

Ernst Schaumann

Papers

Dicyanomethylenethiiranes from Thioketenes and Tetracyanoethylene Oxide.

Lewis Acid Supported Reactions of 1,3‐Bis(silyl)allyl Compounds with Epoxides — Inter‐ and Intramolecular Versions.

Synthesis of 1‐Functionalized Silylcyclopropanes via Cyclization of 3‐Silylalk‐4‐enols.

Cycloadditionsreaktionen von heterokumulenen 3. mitt. thermische cycloadditionsreaktionen von heterokumulenen mit 2-dialkylaminoazirinen

Methyl Shifts in 1,4-Dipoles from Sulfonyl Isocyanates and Ketene O,N-Acetals.