Na2CO3-promoted synthesis of thiocarbamates from isocyanates and thiols under mild conditions

Here, we developed an efficient method for the synthesis of s-alkyl or aryl thiocarbamates catalyzed by Na2CO3 under mild conditions using alkyl or aryl isocyanates and thiophenols or thiols. In situ reaction with deuterated tetrahydrofuran (d8-THF) was carried out to investigate the reaction mechanism. This method has the advantages of high yield, good functional group tolerance and high atom economy.

Electrochemically-driven difunctionalization of the isocyanide and Mumm rearrangement cascade: expeditious synthesis of N-acyl-N-alkyl S-thiocarbamates

We describe the novel electrochemical multicomponent reaction (e-MCR) of readily available isocyanides, thiols and carboxylic acids to form N-substituted S-thiocarbamate derivatives that are found in several biologically active compounds. The effectiveness of the μ-electro flow reactor (μ-EFR) was showcased through significant reduction in electrolyte volume during the reaction, achieving gram-scale production of 4a within a short 12 min residence time using a Pt/Pt flow cell.

Direct C-H Sulfuration: Synthesis of Disulfides, Dithiocarbamates, Xanthates, Thiocarbamates and Thiocarbonates

In light of the important biological activities and widespread applications of organic disulfides, dithiocarbamates, xanthates, thiocarbamates and thiocarbonates, the continual persuit of efficient methods for their synthesis remains crucial. Traditionally, the preparation of such compounds heavily relied on intricate multi-step syntheses and the use of highly prefunctionalized starting materials. Over the past two decades, the direct sulfuration of C-H bonds has evolved into a straightforward, atom- and step-economical method for the preparation of organosulfur compounds. This review aims to provide an up-to-date discussion on direct C-H disulfuration, dithiocarbamation, xanthylation, thiocarbamation and thiocarbonation, with a special focus on describing scopes and mechanistic aspects. Moreover, the synthetic limitations and applications of some of these methodologies, along with the key unsolved challenges to be addressed in the future are also discussed. The majority of examples covered in this review are accomplished via metal-free, photochemical or electrochemical approaches, which are in alignment with the overraching objectives of green and sustainable chemistry. This comprehensive review aims to consolidate recent advancements, providing valuable insights into the dynamic landscape of efficient and sustainable synthetic strategies for these crucial classes of organosulfur compounds.

Iodine-Catalyzed Cascade Annulation of 4-Hydroxycoumarins with Aurones: Access to Spirocyclic Benzofuran-Furocoumarins

An attractive approach for the preparation of spirocyclic benzofuran-furocoumarins has been developed through iodine-catalyzed cascade annulation of 4-hydroxycoumarins with aurones. The reaction involves Michael addition, iodination, and intramolecular nucleophilic substitution in a one-step process, and offers an efficient method for easy access to a series of valuable spirocyclic benzofuran-furocoumarins in good yields (up to 99%) with excellent stereoselectivity. Moreover, this unprecedented protocol provides several advantages, including readily available materials, an environmentally benign catalyst, a broad substrate scope, and a simple procedure.

Isothiocyanates (in situ) and sulfonyl chlorides in water for N-functionalization of bicyclic amidines: access to N-alkylated γ-/ω-lactam derivatized thiourea and sulfonamides

Herein, we showcase the potential of isothiocyanates generated in situ and aryl sulfonyl chlorides as electrophiles in water for N-functionalization of bicyclic amidines (DBN and DBU). This strategy provides complementary access to a range of thiouredosulfides, sulfonamides, aroylthioureas and amides derivativatized with distal γ- and ω-lactams. A novel sulfonyl chloride mediated formation of β-uredo sulfides has been achieved from β-isothiocyanato sulfides, removing the requirement for the harsh synthesis of unstable isocyanates. Mechanistic studies suggest a radical mechanism for the difunctionalization of alkenes, the efficacy of H2O in the ring opening of bicyclic amidines, and an oxygen source along with sulfonyl chloride as desulfurization agents for thiourea to afford urea derivatives.

S-alkyl Dithiocarbamates Synthesis through Electrochemical Multicomponent Reaction of Thiols, Hydrogen Sulfide, and Isocyanides

Dithiocarbamates synthesis is extremely important in plenty of biomedical and agrochemical applications, especially fungicide development, but remains a great challenge. In this work, we have successfully developed a multicomponent reaction protocol to convert H2S into S-alkyl dithiocarbamates under constant current conditions. No additional oxidants nor additional catalysts are required, and due to mild conditions, the reactions display a broad substrate scope, including varieties of thiols or disulfides.

Synthesis of Sulfur-Containing Analogues of Hedychenone, a Labdane Diterpenoid from Hedychium spicatum

The labdane diterpene hedychenone, isolated from Hedychium spicatum, is an example of a furan-containing natural product. Herein, a new and efficient method for the synthesis of 19 new thio analogues of hedychenone is reported. The present methodology exhibits a broad substrate scope with good to excellent yields without metal or base under mild reaction conditions. The natural compound 1 and four semisynthetic derivatives (3a, 3b, 3i, and 3j) exhibited strong α-glucosidase inhibition activity with IC₅₀ values of 15.93 ± 0.29, 9.70 ± 0.33, 11.82 ± 0.06, 12.23 ± 0.33, and 12.15 ± 0.14 μg/mL, respectively. In addition, compound 3e (6.0 ± 0.04 mm; zone of inhibition) displayed antibacterial activity against Staphylococcus aureus. This study increases the chemical diversity of bioactive hedychenone derivatives and provides a direction for the development of antidiabetic agents.

Rationally designed conjugated microporous polymers for efficient photocatalytic chemical transformations of isocyanides

Click-based conjugated microporous polymers have been rationally designed and prepared for efficient N–H insertion like reaction of aryl isocyanides and photosynthesis of thiocarbamates.

Electrochemical metal- and oxidant-free synthesis of S-thiocarbamates

An expeditious synthetic strategy to access functionalized S-thiocarbamates was developed in good to excellent yields and with high current efficiencies. Readily available isocyanides and thiols were used as the starting materials under simple metal- and oxidant-free reaction conditions avoiding an inert atmosphere. The practical application of the present methodology was achieved by electrochemical synthesis of the herbicides prosulfocarb and pebulate. Furthermore, continuous electrochemical flow conditions using a graphite/Pt flow cell were used to obtain S-thiocarbamate compounds on a gram scale within a residence time of 35 min.

Visible-light-promoted synthesis of secondary and tertiary thiocarbamates from thiosulfonates and N-substituted formamides

A general visible-light-promoted metal-free synthesis of secondary and tertiary thiocarbamates starting from thiosulfonates and N-substituted formamides is developed. By employing rhodamine B as a photocatalyst and tert-butyl hydroperoxide (TBHP) as an oxidant, a wide scope of thiocarbamates can be obtained through direct thiolation of acyl C-H bonds under irradiation of blue light at room temperature for 12 h.

Metal-free electrochemical synthesis of α-ketoamides via decarboxylative coupling of α-keto acids with isocyanides and water

A mild and convenient electrochemical protocol has been developed for the preparation of α-ketoamides via a decarboxylative coupling reaction of α-keto acids with isocyanides and water.

Thio radical-induced denitrogenative annulation of 1-azido-2-isocyanoarenes to construct 2-thiolated benzimidazoles

A method for the synthesis of 2-thiolated benzimidazoles is described starting from thiols and 1-azido-2-isocyanoarenes. The isocyano group works as an acceptor of various thio radicals, followed by denitrogenative annulation of the resulting imidoyl radical intermediates to the azido group, with nitrogen loss as the only process involving high bond-forming efficiency. The one-pot method for the synthesis of these products with high functional group tolerance in the benzimidazole-based ring is not available in previous literature.

KI-catalyzed synthesis of S-Thiocarbamates by cross-coupling of cyclohexyl isocyanide with sulfonyl chlorides

A simple and efficient process for direct generation of various S-thiocarbamates is developed by cross-coupling of readily available sulfonyl chlorides with cyclohexyl isocyanide. The yields are excellent and the structures of the generated S-thiocarbamates are characterized by nuclear magnetic resonance spectroscopy, infrared spectroscopy, and high-resolution mass spectrometry together with X-ray crystallographic analysis. The protocol has the advantages of using easily available reagents, employs inexpensive KI as the reagent, demonstrates good functional group tolerance, and utilizes mild reaction conditions.

A novel three-component reaction between isocyanides, alcohols or thiols and elemental sulfur: a mild, catalyst-free approach towards O-thiocarbamates and dithiocarbamates

A new multicomponent reaction has been developed between isocyanides, sulfur and alcohols or thiols under mild reaction conditions to afford O-thiocarbamates and dithiocarbamates in moderate to good yields. The one-pot reaction cascade involves the formation of an isothiocyanate intermediate, thus a catalyst-free synthesis of isothiocyanates, as valuable building blocks from isocyanides and sulfur is proposed, as well. The synthetic procedure suits the demand of a modern organic chemist, as it tolerates a wide range of functional groups, it is atom economic and easily scalable.

Iodine-Catalyzed Odorless Synthesis of S-Thiocarbamates with Sulfonyl Chlorides as a Sulfur Source

A general and efficient protocol for the direct preparation of various S-thiocarbamates with readily available and inexpensive sulfonyl chlorides as an odorless sulfur source was developed. The employment of easily available reactants, excellent functional group tolerability, and mild reaction conditions make this process very practical.

Metal-Free Catalytic Synthesis of Thiocarbamates Using Sodium Sulfinates as the Sulfur Source

A novel molecular iodine-catalyzed protocol for the construction of thiocarbamates from readily available sodium sulfinates, isocyanides, and water has been described. The present methodology offers a facile and practical route to a variety of thiocarbamates in moderate to good yields with favorable functional group tolerance by use odorless sodium sulfinates as the sulfur source. The mechanistic studies suggest the present transformation involves a radical process.

Synthesis of quinazoline-3-oxides via a Pd(ii) catalyzed azide-isocyanide coupling/cyclocondensation reaction

A novel and efficient protocol concerning palladium catalyzing the three-component reaction of 2-azidobenzaldehyde, isocyanide, and hydroxylamine hydrochloride is developed. This method allows the rapid elaboration of quinazoline 3-oxides in a one-pot fashion. The 3-CR mainly involves concatenation of azide-isocyanide denitrogenative coupling, condensation with hydroxylamine and 6-exo-dig cyclization. The salient features of the methodology are operational simplicity, use of milder reaction conditions, being devoid of any additives such as oxidants (redox neutral) or base, and releasing N2 and H2O as the byproducts.