[1 + 2] Cycloadditions of Sulfur Monoxide (SO) to Alkenes and Alkynes and [1 + 4] Cycloadditions to Dienes (Polyenes). Generation and Reactions of Singlet SO?

Synthesis of Thiourea and Thioamide S-Oxides via SO Transfer from a Thiirane S-Oxide onto N-Heterocyclic Carbenes

Thiourea S-oxides are labile compounds that suffer from a quick overoxidation when directly prepared from thioureas. Therefore, we have developed an alternative route on the basis of the SO transfer from a thiirane S-oxide onto sterically encumbered N-heterocyclic carbenes, including imidazole- and imidazoline-ylidenes, and a cyclic alkyl amino carbene. Reaction conditions and DFT computations suggest a concerted SO transfer mechanism. Thiourea S-oxides are nucleophiles adding to dimethyl acetylenedicarboxylate under fission of the S-O bond.

A Sulfur Monoxide Surrogate Designed for the Synthesis of Sulfoxides and Sulfinamides

Sulfur monoxide (SO) is a highly reactive species that cannot be isolated in bulk. However, SO can play a pivotal role as a fundamental building block in organic synthesis. Reported herein is the design and application of a sulfinylhydrazine reagent as an easily prepared sulfur monoxide surrogate. We show facile thermal SO transfer from this reagent to dienes where a reaction using a mechanistic probe suggests the generation of singlet SO. Combined with Grignard reagents and appropriate carbon or nitrogen electrophiles, the reagent serves as an effective "SO" donor to enable the one-pot, three-component synthesis of sulfoxides and sulfinamides.

Double Bond Cleavage in Small Molecules Using a Geminal Sc/P Lewis Pair

Frustrated Lewis pairs (FLPs) have proven capable of cleaving the H-H σ-bond and binding a variety of unsaturated small molecules. In contrast, examples of FLP-mediated complete rupture of double-bonded substrates remain scarce. Herein, we present a geminal Sc/P Lewis pair, i.e., (ArO)2ScN(tBu)PPh2 (Ar = 2,6-tBu2-C6H3), that exhibits typical FLP-type 1,2-addition reactivity toward CO2. Notably, it enables the complete cleavage of a series of double bonds, such as the N═N bond in azobenzene or pyridazine, the N═O bond in nitrosobenzene, and the N═S and S═O bonds in N-sulfinylaniline, to yield the corresponding metallacyclic products. Moreover, the first rare-earth metal sulfur monoxide adduct could be obtained through the bond cleavage of PhNSO, demonstrating the capability of rare-earth metal complexes to capture reactive species.

Monooxygenase- and Dioxygenase-Catalyzed Oxidative Dearomatization of Thiophenes by Sulfoxidation, cis-Dihydroxylation and Epoxidation

Enzymatic oxidations of thiophenes, including thiophene-containing drugs, are important for biodesulfurization of crude oil and drug metabolism of mono- and poly-cyclic thiophenes. Thiophene oxidative dearomatization pathways involve reactive metabolites, whose detection is important in the pharmaceutical industry, and are catalyzed by monooxygenase (sulfoxidation, epoxidation) and dioxygenase (sulfoxidation, dihydroxylation) enzymes. Sulfoxide and epoxide metabolites of thiophene substrates are often unstable, and, while cis-dihydrodiol metabolites are more stable, significant challenges are presented by both types of metabolite. Prediction of the structure, relative and absolute configuration, and enantiopurity of chiral metabolites obtained from thiophene enzymatic oxidation depends on the substrate, type of oxygenase selected, and molecular docking results. The racemization and dimerization of sulfoxides, cis/trans epimerization of dihydrodiol metabolites, and aromatization of epoxides are all factors associated with the mono- and di-oxygenase-catalyzed metabolism of thiophenes and thiophene-containing drugs and their applications in chemoenzymatic synthesis and medicine.

Sulfur monoxide thermal release from an anthracene-based precursor, spectroscopic identification, and transfer reactivity

Sulfur monoxide (SO) is a highly reactive molecule and thus, eludes bulk isolation. We report here on synthesis and reactivity of a molecular precursor for SO generation, namely 7-sulfinylamino-7-azadibenzonorbornadiene (1). This compound has been shown to fragment readily driven by dinitrogen expulsion and anthracene formation on heating in the solid state and in solution, releasing SO at mild temperatures (<100 °C). The generated SO was detected in the gas phase by MS and rotational spectroscopy. In solution, 1 allows for SO transfer to organic molecules as well as transition metal complexes.

The near-UV absorber OSSO and its isomers

The enigmatic near-UV absorber, OSSO, in the yellowish atmosphere of Venus and three novel isomers have been spectroscopically characterized.

Crystalline, room-temperature stable phosphine–SO2 adducts: generation of sulfur monoxide from sulfur dioxide

Particularly basic phosphines form isolable Lewis base adducts with SO₂ that readily release SO at room temperature driven by the formation of the corresponding phosphine oxides.

Extensive theoretical study on electronically excited states and predissociation mechanisms of sulfur monoxide including spin-orbit coupling

The potential energy curves of the 69 Ω states generated from the 24 Λ-S states of sulfur monoxide are calculated for the first time using the internally contracted multireference configuration interaction method with the Davidson correction and the entirely uncontracted aug-cc-pV5Z basis set. Spin-orbit coupling is taken into account by the state interaction approach with the full Breit-Pauli Hamiltonian. Very good agreement is achieved between our computed spectroscopic properties and the available experimental data. The transition properties of the B(3)Σ(-) -X(3)Σ(-) and (4)1-X0(+) transitions are predicted, and our computed Franck-Condon factors and radiative lifetimes match the experimental results very well. The predissociation mechanisms are investigated, and various new predissociation channels are located. We present a new interpretation on the breaking-off of the rotational levels of the B(3)Σ(-) lower vibrational states observed in experiment, and propose that the predissociation is induced by the Coriolis coupling between the B(3)Σ(-) rovibrational levels and the A(3)Π state. Our calculations indicate that, at ν' = 9, the B(3)Σ(-) state predissociates via the C(3)Π state; around ν' = 14, three spin-orbit-induced predissociation pathways via (1)(5)Σ(+) , (2)(5)Π, and e(1)Π would be open; around ν' = 17, the pathways via (2)(1)Σ(+) , (2)(3)Σ(+) and (2)(5)Σ(+) would contribute. These satisfactorily explain the experimental results about the diffuseness of the B(3)Σ(-) bands. Furthermore, various predissociation pathways of the C'(3)Π state are predicted, through which the C'(3)Π state could predissociate rapidly.

One-pot oxidation and protonation of a bridging sulfide and rare crystallographic evidence of a coordinated [SO] complex in [Pt2(micro-S2O2H)(PPh3)4]+

One-pot oxidation and protonation of the sulfide bridging complex [Pt(2)(micro-S)(2)(PPh(3))(4)] can be promoted by lanthanide or scandium compounds, leading to the isolation of [Pt(2)(micro-S(2)O(2)H)(PPh(3))(4)](+); crystallographic elucidation confirmed sulfide mono-oxygenation without S-S bonding to give formally [SO](2-) in the form of an [SOHOS](3-) overhead bridge.