Base-Induced Sulfoxide-Sulfenate Rearrangement of 2-Sulfinyl Dienes for the Regio- and Stereoselective Synthesis of Enantioenriched Dienyl Diols.

The base-induced [2,3]-sigmatropic rearrangement of a series of enantiopure 2-sulfinyl dienes has been examined and optimized using a combination of NaH and PrOH. The reaction takes place by allylic deprotonation of the 2-sulfinyl diene to give a bis-allylic sulfoxide anion intermediate that after protonation undergoes sulfoxide-sulfenate rearrangement. Different substitution at the starting 2-sulfinyl dienes has allowed us to study the rearrangement finding that a terminal allylic alcohol is determinant to achieve complete regioselectivity and high enantioselectivities (90:10-95:5) with the sulfoxide as the only element of stereocontrol.

Enantioselective Suzuki cross-coupling of 1,2-diboryl cyclopropanes.

Herein, we describe the catalytic enantioselective cross-coupling of 1,2-bisboronic esters. Prior work on group specific cross coupling is limited to the use of geminal bis-boronates. This desymmetrization provides a novel approach to prepare enantioenriched cyclopropyl boronates with three contiguous stereocenters, that could be further derivatized through selective functionalization of the carbon-boron bond.

Sulfinyl-Mediated Stereoselective Functionalization of Acyclic Conjugated Dienes.

The chemo- and stereocontrolled functionalization of conjugated sulfinyl dienes in a cascade process that involves a conjugate addition, diastereoselective protonation and a [2,3]-sigmatropic rearrangement is reported. Enantioenriched 1,4-diol and 1,4-aminoalcohol derivatives are obtained in a very straightforward manner. Further functionalization of these structures, including highly stereoselective epoxidation, dihydroxylation and the stereodivergent synthesis of several polyols in a controlled fashion is described.

From Allylic Sulfoxides to Allylic Sulfenates: Fifty Years of a Never-Ending [2,3]-Sigmatropic Rearrangement.

The [2,3]-sigmatropic rearrangement of allylic sulfoxides to allylic sulfenates is a reversible process, generally shifted toward the sulfoxide. In the presence of thiophiles, the sulfenate is trapped, and allylic alcohols are obtained under mild conditions. In most cases, a good transfer of stereochemical information through an ordered transition state is obtained.

Chiral Sulfur Functional Groups as Definers of the Chirality at the Metal in Ir and Rh Half-Sandwich Complexes: A Combined CD/X-ray Study.

Mesoionic carbenes (MICs) derived from triazolium salts that contain chiral sulfoxide or sulfoximine functional groups were used to construct enantiopure chiral-at-metal Ir and Rh half-sandwich complexes through the synthetic sequence of MIC complexation/C-H aromatic activation. The process was efficient and diastereoselective for the formation of enantiopure five-membered metallacycles. The use of the enantiomers of the chiral sulfur groups allowed us to prepare complexes that had opposite configurations at the metal center.

Gold(I)-Catalyzed Cycloisomerization-Dimerization Cascade of Benzene-Tethered 1,6-Enynes.

An unprecedented stereoselective domino reaction of 1,6-enynes with an aryl ring at C3-C4 in the presence of gold(I) catalysts at low temperature is described. This process involves a novel 5-exo-dig cycloisomerization-dimerization sequence to afford formal Diels-Alder adducts that undergo a smooth gold-catalyzed double bond migration at room temperature. In addition, the first examples of the gold mesoionic carbene mediated [2+2+2] cycloaddition of these enynes with benzaldehyde are reported.

Sulfur Groups Improve the Performance of Triazole- and Triazolium-Based Interaction Units in Anion Binding.

An NMR comparative study of 1,2,3-triazole and triazolium anion recognition units containing sulfoxide, sulfone, and sulfoximine groups at C unveils an enhancement in binding ability up to ≈1 kcal/mol in acetone-d correlated with a theoretical increase of H acidity. DFT calculations provide insight into binding modes in line with experimental data for these receptors.

Desulfinylation of Ag(I) Sulfinyl Mesoionic Carbenes: Preparation of C-Unsubstituted Au(I)-1,2,3-Triazole Carbene Complexes.

New and well-characterized Ag-bis(1,2,3-triazolylidene) complexes having enantiopure (S)-sulfoxides upon sequential treatment with alcohols and Au(I) form separable mixtures of regioisomeric C-unsubstituted Au-1,2,3-triazolylidene complexes. Mechanistic studies and DFT calculations support a desulfinylation process for in situ generated free triazolylidene salts.

Gold Sulfinyl Mesoionic Carbenes: Synthesis, Structure, and Catalytic Activity.

Gold mesoionic carbenes having a chiral sulfoxide group attached to the C4 position of the five membered ring have been prepared and tested as catalysts in the cycloisomerization of enynes. These new catalysts are very efficient, with the sulfoxide moiety playing a key role in their activity and the N1-substituent in control of the regioselectivity of these processes.

Sulfinyl-Mediated Stereoselective Overman Rearrangements and Diels-Alder Cycloadditions.

Sulfinyl trichloroacetamides are readily obtained in excellent yields through a highly stereoselective Overman rearrangement. Related bis-allylic substrates lead to amido 2-sulfinyl butadiene derivatives in excellent yields, with total chemo- and diastereoselectivity. These amido dienyl sulfoxides undergo highly selective Diels-Alder cycloadditions with N-phenylmaleimide with remarkable stereocontrol by the sulfoxide moiety.

Synthesis of Enantiopure 3-Hydroxypiperidines from Sulfinyl Dienyl Amines by Diastereoselective Intramolecular Cyclization and [2,3]-Sigmatropic Rearrangement.

The highly diastereoselective base-promoted intramolecular cyclization of a variety of enantiopure sulfinyl dienyl amines provides novel sulfinyl tetrahydropyridines that are readily converted to 3-hydroxy tetrahydropyridines via sigmatropic rearrangement. The influence of N- and C- substituents on the process has been studied. Procedures to shorten the sequence such as the tandem cyclization followed by [2,3]-sigmatropic rearrangement, as well as cyclization of the free amine, under Boc- or ArSO- deprotection conditions have been examined.

Remote stereocontrol in the synthesis of acyclic 1,4-diols and 1,4-aminoalcohols from 2-sulfinyl dienes.

The highly diastereoselective conjugate addition of alcohols and amines (RXH) to enantiopure 2-sulfinyl dienes renders transient allylic sulfoxides which undergo sulfoxide-sulfenate rearrangement and sulfenate cleavage providing 2-ene-1,4-diols and 2-ene-1,4-aminoalcohols with up to 99:1 dr. The method allows for the generation of two stereocenters in a single synthetic operation with remote chirality transfer of one center into the other.

Sulfoxide-directed enantioselective synthesis of functionalized tetrahydropyridines.

The highly selective base-promoted cyclization of enantiopure sulfinyl dienamines provides stereodefined sulfinyl 1,2,3,6-tetrahydropyridines (dr up to 99:1). Subsequent sigmatropic rearrangement affords tetrahydropyridin-3-ols in good yields and selectivities.

Sulfinyl-mediated stereoselective Overman rearrangements and Diels-Alder cycloadditions.

The Overman rearrangement of allylic sulfinyl trichloroacetimidates affords sulfinyl trichloroacetamides with high stereoselectivity and excellent yields. Bis-allylic substrates lead to amido 2-sulfinyl butadiene derivatives in excellent yields, with total chemo- and diastereoselectivity. The Diels-Alder cycloaddition of related dienes is controlled by the sulfoxide moiety.

An approach to the stereoselective synthesis of enantiopure dihydropyrroles and aziridines from a common sulfinyl-sulfinamide intermediate.

The diastereoselective addition of lithiated vinyl sulfoxides to enantiopure sulfinimines provides direct access to a wide assortment of allylic sulfinamides in good yields and excellent selectivities. These adducts are key precursors to differently functionalized cis- and trans-dihydropyrroles. Modulation of the protecting group on nitrogen prior to cyclization has a significant impact on the stereochemical outcome, allowing for the selective preparation of 2,5-cis- or 2,5-trans-3-sulfinyl disubstituted dihydropyrroles from a common sulfinamide intermediate.

Enantiopure 1,4-diols and 1,4-aminoalcohols via stereoselective acyclic sulfoxide-sulfenate rearrangement.

Treatment of acyclic α-hydroxy and α-tosylamino sulfinyl dienes with amines affords enantiopure 1,4-diol or 1,4-hydroxysulfonamide derivatives in good yields and diastereoselectivities. This one-pot procedure entails a conjugate addition that triggers a diastereoselective sulfoxide-sulfenate [2,3]-sigmatropic rearrangement.

Development of chromanes as novel inhibitors of the uncoupling proteins.

The uncoupling proteins (UCPs) are mitochondrial carriers that modulate the energetic efficiency and, as a result, can lower superoxide levels. Here, we describe the discovery of a small-molecule inhibitor of the UCPs. Screening of potential UCP1 regulators led to the identification of chromane derivatives that inhibit its proton conductance.

Development of molecular probes for the human 5-HT(6) receptor.

In this work we report the synthesis of a set of labeled ligands targeting the human 5-HT(6) receptor (h5-HT(6)R). Among the synthesized compounds, fluorescent probe 10 (K(i) = 175 nM and Φ(f) = 0.21) and biotinylated derivative 15 (K(i) = 90 nM) deserve special attention because they enable direct observation of the h5-HT(6)R in cells.

Development of Fluorescent Ligands for the Human 5-HT1A Receptor.

In this work, we report the design and synthesis of a set of fluorescent probes targeting the human 5-HT1A receptor (h5-HT1AR). Among the synthesized compounds, derivative 4 deserves special attention as being a high-affinity ligand (K i = 2 nM) with good fluorescent properties (I em > 1000 au and a fluorescence quantum yield, Φf, of 0.26), which enables direct observation of the h5-HT1AR in cells.

Sulfoxide-directed intramolecular [4 + 2] cycloadditions between 2-sulfinyl butadienes and unactivated alkynes.

Sulfinyl dienynes undergo thermal and catalyzed IMDA cycloadditions, often at room temperature, to produce cyclohexa-1,4-dienes with good yields and high selectivities. Additionally, the products preserve a synthetically useful vinyl sulfoxide functionality. The selective manipulation of the double bonds in the cycloadducts has also been examined in this work.

Asymmetric Claisen rearrangements on chiral vinyl sulfoxides.

Highly diastereoselective Claisen rearrangements of acyclic allyl vinyl ethers bearing a chiral sulfoxide at C-5 provide gamma-delta-unsaturated aldehydes or ketones with up to two consecutive asymmetric centers in the molecule whilst preserving a useful vinyl sulfoxide. The reactivity of related vinyl sulfides and sulfones has also been examined in this work.

Highly diastereoselective Katsuki-Jacobsen oxidation-epoxidation of alpha-silyloxy sulfinyl dienes: synthetic applications.

Katsuki-Jacobsen oxidation-epoxidation of acyclic alpha-silyloxy sulfinyl dienes, followed by acid-promoted cyclization, leads to 2,5-trans-sulfonyl dihydrofurans with good selectivities. As an application, the formal syntheses of (6S,7S,9R,10R)- and (6S,7S,9S,10S)-6,9-epoxynonadec-18-ene-7,10-diols is reported.

[2,3]-Sigmatropic rearrangements of 3-sulfinyl dihydropyrans: application to the syntheses of the cores of ent-dysiherbaine and deoxymalayamicin A.

The [2,3]-sigmatropic rearrangement of a variety of configurationally stable diastereomeric allylic sulfinyl dihydropyrans, produced by base-promoted cyclization of sulfinyl dienols, has been studied. In some cases, the efficient transformation of these substrates into dihydropyranols required an in-depth study of reaction conditions, with the preferred protocol relying on the use of DABCO in warm toluene. This methodology has been applied to the syntheses of the cores of ent-dysiherbaine and deoxymalayamicin A by means of efficient tethered aminohydroxylations.