One-Pot Sulfoxide Synthesis Exploiting a Sulfinyl-Dication Equivalent Generated from a DABSO/Trimethylsilyl Chloride Sequence.

A one-pot process for the synthesis of unsymmetrical sulfoxides using organometallic nucleophiles is described. Sulfur dioxide, delivered from the surrogate DABSO (DABCO-bis(sulfur dioxide)), acts as the initial electrophile and combines with the first organometallic reagent to generate a sulfinate intermediate. In situ conversion of the sulfinate to a sulfinate silyl ester, using TMS-Cl (trimethylsilyl chloride), generates a second electrophile, allowing addition of a second organometallic reagent.

Autocatalytic intermolecular versus intramolecular deprotonation in C-H bond activation of functionalized arenes by ruthenium(II) or palladium(II) complexes.

The activation of the C-H bond of 1-phenylpyrazole (2) and 2-phenyl-2-oxazoline (3) by [Ru(OAc)2(p-cymene)] is an autocatalytic process catalyzed by the co-product HOAc. The reactions are indeed faster in the presence of acetic acid and water but slower in the presence of a base K2CO3. A reactivity order is established in the absence of additives: 2-phenylpyridine>2-phenyl-2-oxazoline>1-phenylpyrazole (at RT).

Catalytic intermolecular allyl-allyl cross-couplings between alcohols and boronates.

We developed catalytic intermolecular C(sp(3))-C(sp(3)) cross-couplings between various allyl alcohols and allyl boronates, which proceeded smoothly in the presence of nickel(0) under mild conditions to form 1,5-dienes with excellent linear- and γ-selectivity; the use of boronates proved to be crucial in terms of reactivity.

Autocatalysis for C-H bond activation by ruthenium(II) complexes in catalytic arylation of functional arenes.

Kinetic data for the C-H bond activation of 2-phenylpyridine by Ru(II)(carboxylate)(2)(p-cymene) I (acetate) and I' (pivalate) are available for the first time. They reveal an irreversible autocatalytic process catalyzed by the coproduct HOAc or HOPiv (acetonitrile, 27 °C). The overall reaction is indeed accelerated by the carboxylic acid coproduct and water.

Palladium(0) versus nickel(0) catalysis in selective functional-group-tolerant sp(3)-sp(3) carbon-carbon bond formations.

We have uncovered Pd(0)-catalyzed intermolecular nonsymmetrical Suzuki-Miyaura-type sp(3)-sp(3) C-C bond formations between allyl carbonates and nontoxic allyl, allenyl, or propargyl boronates. This report represents the first use of these types of boronic esters in this particular context. The present transformations proceeded with high selectivity under remarkably mild conditions, and various functional groups including an aldehyde function proved to be compatible.

Direct arylation of oxazoles at C2. A concise approach to consecutively linked oxazoles.

The synthesis of bis- and trisoxazoles via direct arylation is discussed. A variety of aryl groups can be installed at the 2-position of 5-aryl and 5-carboxy-substituted oxazoles under mild conditions using palladium catalysis on water. The direct arylation method can be extended to the synthesis of bis- and trisoxazoles if 2-triisopropylsilyl-4-iodooxazole is used as the electrophile in the arylation.

Regioselective palladium cross-coupling of 2,4-dihalooxazoles: convergent synthesis of trisoxazoles.

A regioselective Suzuki-Miyaura cross-coupling of 2,4-dihalooxazoles followed by a Stille coupling has been successfully developed. The procedure affords convergent syntheses of trisoxazoles in high yield and in a minimum number of steps.

Suzuki coupling of oxazoles.

A protocol for the functionalization of the oxazole 2- and 4-positions using the Suzuki coupling reaction is described. 2-Aryl-4-trifloyloxazoles undergo rapid, microwave-assisted coupling with a range of aryl and heteroaryl boronic acids in good to excellent yields. The methodology is similarly effective using 4-aryl-2-chlorooxazoles as the coupling partner and has been extended to the synthesis of a novel class of homo- and heterodimeric 4,4-linked dioxazoles.