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 title compounds are prepared by an efficient one-pot reaction using readily available phosphonates and S-alkyl carbonchloridothioates. The reaction is capable of variation in the phosphonate and especially in the carbanochloridothioate components

Synthesis of α,β-unsaturated thiocarboxylic acid S-esters via Horner-Emmons olefination

An efficient synthesis of 4-thioxocyclobut-2-enones by the action of 0.5 molar equivalents of Lawesson's reagent on the corresponding diones is reported.

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Highly Regioselective Monothionation of Squaric and Semisquaric Acid Derivatives

The higher excited-state reactions of sterically encumbered thioketenes la-d in solution were investigated. Substituted thiiranes, thio esters, thioacetophenones, and 1,2-diones are formed on photoexcitation of thioketenes in hydroxylic and nonhydroxylic solvents. Thioketenes while unreactive upon excitation to $S_1$ produce thiiranylidene carbene and zwitterionic intermediates upon excitation to $S_2$. The reactive state is identified to be $S_2 (\pi \pi^*)$. The excited thioketene resists carbon monosulfide elimination but undergoes rearrangement. The photobehavior of thioketenes, established in solution for the first time, differs significantly from that of ketenes, and it cannot be extrapolated from that of structurally analogous ketenes and allenes.

Ernst Schaumann

Papers

Synthesis of α,β-unsaturated thiocarboxylic acid S-esters via Horner-Emmons olefination

Highly Regioselective Monothionation of Squaric and Semisquaric Acid Derivatives

Photochemical behavior of thioketenes in solution: reaction from S2

Synthese von rac-Norartemeseol

The crystal and molecular structure of the cycloadduct from an activated carbodiimide and methyl isothiocyanate