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

Thioketyls. 3. Radical anions of thioketenes

(2+1) Cycloaddition of chloro(phenylthio)carbene to vinyl silanes. A facile synthesis of highly functionalized cyclopropanes

Konkurrenz zwischen 1,2- un 1,3-ringöggnung in der umsetzung von 3-dimethylamino-2-phenyl-2H-azirinen mit kohlenstoffdisulfid

Elektronenacceptoren in der 2-Stellung des Allylrests von Alkinyl(allyl)sulfiden 4, 11, 15 begunstigen die Thio-Claisen-Umlagerung zu Thioketenen 5, 12, 16, behindern sie aber in der 3-Stellung. Fur den Substituenten der Dreifachbindung gilt die Reihenfolge Silyl > Alkyl > Alkylthio. Die Ergebnisse lassen sich durch eine dipolare Zwischenstufe 19 bzw. einen stark polarisierten Ubergangszustand der Umlagerung verstehen.



Thioketene Syntheses, VII, Substituent Effects on the Thio-Claisen Rearrangement of Alkynyl Allyl Sulfides



Electron acceptors in the position 2 of the allyl residues in alkynyl allyl sulfides 4, 11, 15 favor the Thio-Claisen rearrangement to give thioketenes 5, 12, 16, but in position 3 impede the reaction. For the substituent on the triple bond, the sequence silyl > alkyl > alkylthio is valid. The results can be understood in terms of a zwitterionic intermediate 19 or a highly polarized transition state of the rearrangement.

Ernst Schaumann

Papers

Thioketyls. 3. Radical anions of thioketenes

(2+1) Cycloaddition of chloro(phenylthio)carbene to vinyl silanes. A facile synthesis of highly functionalized cyclopropanes

Konkurrenz zwischen 1,2- un 1,3-ringöggnung in der umsetzung von 3-dimethylamino-2-phenyl-2H-azirinen mit kohlenstoffdisulfid

Thioketen‐Synthesen, VII. Substituenteneffekte auf die Thio‐Claisen‐Umlagerung von Alkinyl(allyl)sulfiden

Organylthio(silyl)carbenes