Reactions of thiocarbonyl compounds with electrophilic and nucleophilic carbenes as well as with their metal complexes

Abstract

A variety of cyclic and acyclic products are reported for reactions of thiocarbonyl compounds with carbenes and their metal complexed derivatives. Electrophilic and nucleophilic carbenes react with non-enolizable thioketones yielding thiocarbonyl ylides or 1,3-zwitterions, respectively, as plausible, reactive intermediates. In most cases, the initially formed intermediates undergo 1,3-electrocyclization yielding respective thiiranes, which, depending on the substitution pattern, are either isolated as final products or extrude elemental sulfur forming substituted ethylene derivatives. In addition, reactive thiocarbonyl ylides formed from -oxo substituted carbenoids after the thiophilic attack onto the C = S bond undergo competitive 1,3-versus 1,5-dipolar electrocyclization leading to thiiranes or 1,3-oxathioles, respectively. From the point of view of potential practical applications (coordination chemistry, organometallic chemistry, polymer chemistry), zwitterionic hetarylidene dithiocarboxylates accessible as stable 1:1 adducts from the reactions of nucleophilic heterocyclic carbenes (NHCs) with carbon disulfide are of great interest.

A DFT Study on the Molecular Mechanism of Additions of Electrophilic and Nucleophilic Carbenes to Non-Enolizable Cycloaliphatic Thioketones

“…Obtained results allow us to better understand mechanisms of reactions of carbenes with thiocarbonyl compounds leading to thiiranes or products of their secondary conversions [40]. In addition, they nicely complement experimental observations on appearance of reactive thiocarbonyl S-methanides (thiocarbonyl ylides) in reactions of nonenolizable thioketones with electrophilic methylene [:CH 2 ] carried out in low-temperature Ar-matrices [59].…”

“…For reactions of thioketone and with carbene species, two competitive mechanisms can be considered (Scheme 3). In the first case (route A), the formation of the thiirane ring occurs via stepwise mechanism, with the intervention of thiocarbonyl ylide as a reactive intermediate [40]. Alternatively (route B), the thiirane ring can be formed according to the one-step [2 + 1] cycloaddition scheme [26,41].…”

“…In the first step, the reaction occurs via TS1A transition state, and its form accompanied by an increase of the Gibbs free energy of the reaction system 10kcal/mol. Within this TS, a single new ϭ bond is formed between C(1) and S(2) occurs via stepwise mechanism, with the intervention of thiocarbonyl ylide as a reactive intermediate [40]. Alternatively (route B), the thiirane ring can be formed according to the one-step [2 + 1] cycloaddition scheme [26,41].…”

Detection of Ylide Formation between an Alkylidenecarbene and Acetonitrile by Femtosecond Transient Absorption Spectroscopy

“…"Saturated" electrophilic singlet carbenes (1), endowed with an empty p-orbital on the formally sp 2 -hybridized divalent and neutral carbon atom, are known to accept an electron pair from heteroatom-containing moieties (e.g., 2) to form the corresponding ylides (3) (Scheme 1). 1−14 These carbenederived ylides have proven to be of considerable synthesis value, 15−27 and in many instances, they have been directly observed and spectroscopically characterized.…”

Asymmetric Catalytic (2+1) Cycloaddition of Thioketones to Synthesize Tetrasubstituted Thiiranes

“…The cycloaddition of thioketones [5] with diazo compounds provides a direct route for the construction of multisubstituted thiiranes and other S ‐heterocycles (Scheme 1d) [6] . The first reaction of diazomethane with aromatic thioketone was discovered dating back to a century ago, [7] and the mechanism was elucidated by Huisgen later [6c,d] . It is suggested that the reaction occurs via an initial [3+2]‐cycloaddition, followed by the release of N 2 to give thiocarbonyl ylide as key intermediate (path a) [8] .…”