Site-selective and stereoselective functionalization of non-activated tertiary C-H bonds.

The synthesis of complex organic compounds usually relies on controlling the reactions of the functional groups. In recent years, it has become possible to carry out reactions directly on the C-H bonds, previously considered to be unreactive. One of the major challenges is to control the site-selectivity because most organic compounds have many similar C-H bonds.

Direct spectroscopic characterization of a transitory dirhodium donor-acceptor carbene complex.

A multitude of organic transformations catalyzed by dirhodium(II) (Rh2) complexes are thought to proceed via the intermediacy of highly reactive, electrophilic carbenoid intermediates that have eluded direct observation. Herein, we report the generation of a metastable Rh2-carbenoid intermediate supported by a donor-acceptor carbene fragment. This intermediate is stable for a period of ~20 hours in chloroform solution at 0°C, allowing for an exploration of its physical and chemical properties.

Scope and mechanistic analysis of the enantioselective synthesis of allenes by rhodium-catalyzed tandem ylide formation/[2,3]-sigmatropic rearrangement between donor/acceptor carbenoids and propargylic alcohols.

Rhodium-catalyzed reactions of tertiary propargylic alcohols with methyl aryl- and styryldiazoacetates result in tandem reactions, consisting of oxonium ylide formation followed by [2,3]-sigmatropic rearrangement. This process competes favorably with the standard O-H insertion reaction of carbenoids. The resulting allenes are produced with high enantioselectivity (88-98% ee) when the reaction is catalyzed by the dirhodium tetraprolinate complex, Rh(2)(S-DOSP)(4).

D2-symmetric dirhodium catalyst derived from a 1,2,2-triarylcyclopropanecarboxylate ligand: design, synthesis and application.

Dirhodium tetrakis-(R)-(1-(4-bromophenyl)-2,2-diphenylcyclopropanecarboxylate) (Rh(2)(R-BTPCP)(4)) was found to be an effective chiral catalyst for enantioselective reactions of aryl- and styryldiazoacetates. Highly enantioselective cyclopropanations, tandem cyclopropanation/Cope rearrangements and a combined C-H functionalization/Cope rearrangement were achieved using Rh(2)(R-BTPCP)(4) as catalyst. The advantages of Rh(2)(R-BTPCP)(4) include its ease of synthesis, its tolerance to the size of the ester group in the styryldiazoacetates, and its compatibility with dichloromethane as solvent.

Vinyl diazophosphonates as precursors to quaternary substituted indolines and cyclopentenes.

Vinyl diazophosphonates can be stereoselectively synthesized and, depending upon their substitution pattern, undergo intramolecular C-H insertion reactions or sulfonium ylide rearrangements when exposed to Rh(2)(OAc)(4).

Amino acid-derived iodobenzene dicarboxylates: reagents for oxidative conversion of alkenes to amino acid esters.

[reaction: see text] New amino acid-derived iodobenzene dicarboxylates were prepared by the reaction of (diacetoxyiodo)benzene with N-protected natural amino acids. These compounds in the presence of iodide anion can be used as reagents for beta-iodocarboxylation of alkenes leading to the respective amino acid esters.

Synthesis and structure of amino acid-derived benziodazoles: new hypervalent iodine heterocycles.

New N-functionalized benziodazoles were prepared by the peracetic oxidation of 2-iodobenzamides derived from alanine or valine. X-ray crystal structural analysis of two benziodazole-based phenyliodonium derivatives provides insight into facile interchange between benziodazoles and iminium benziodoxoles under acidic or basic conditions. [reaction: see text]