Conversion of some substituted phenols to the corresponding masked thiophenols, synthesis of a dinickel(II) dithiolate macrocyclic complex and isolation of some metal- and ligand-based oxidation products

An Electrocatalytic Newman–Kwart-type Rearrangement

“…Important parts of this development are the exploration of the microwave-assisted NKR, and of the use of a continuous flow reactor under supercritical conditions. , Other approaches are based on the use of catalysts in order to lower reaction temperatures. In some examples, the addition of catalytic amounts of BF 3 ·OEt 2 helped to lower the reaction temperature and to improve the yields, whereby the catalytic effect did not turn out to be general . A catalytic system with a broader scope was introduced in 2009 by Lloyd-Jones et al, who demonstrated that the use of palladium bis­(tri- tert -butylphosphine) allows for conversion of several para- substituted substrates 2 to the corresponding NKR products at 100 °C …”

“…In some examples, the addition of catalytic amounts of BF 3 • OEt 2 helped to lower the reaction temperature and to improve the yields, whereby the catalytic effect did not turn out to be general. 11 A catalytic system with a broader scope was introduced in 2009 by Lloyd-Jones et al, who demonstrated that the use of palladium bis(tri-tert-butylphosphine) allows for conversion of several para-substituted substrates 2 to the corresponding NKR products at 100 °C. 12 A subsequent report by Nicewicz et al showed that the rearrangement can even be achieved at room temperature using a photochemical approach: Upon irradiation with blue LEDs in the presence of a pyrylium-based photoredox catalyst (see Figure 1), a number of substrates 2 having electrondonating groups in ortho-and/or para-position were successfully subjected to NKR.…”

The Newman–Kwart Rearrangement of O‐Aryl Thiocarbamates: Substantial Reduction in Reaction Temperatures through Palladium Catalysis

“…Thermally induced O Ar !S Ar migration in aryl thiocarbamates (1!2, Scheme 1) [1] is commonly referred to [2] as the Newman-Kwart rearrangement ("NKR") [3] and belongs to a group of rearrangements that generate Ar-S/N compounds from phenols. [4] Of these, only the NKR has been extensively utilized, [1] with applications as broad-ranging as medicinal chemistry, [5] chiral ligand synthesis, [6] supramolecular chemistry, [7] molecular switches, [8] molecular rods, [9] dendrimers, [10] organocatalysts [11] and helicenes. [12] The NKR has also been applied industrially, [1,5] more recently by applying microwave [13, 14a] and flow-reactor technologies.…”

“…The [Pd(tBu 3 P) 2 ] catalyst was tested with a small range of simple aryl thiocarbamates (1 a-h, 100 8C, toluene, Table 1, entries [5][6][7][8][9][10][11]. In all cases rearrangement was catalyzed, allowing NKR at a substantially lower temperature than that required for the standard thermal conditions.…”

Electrochemically Catalyzed Newman–Kwart Rearrangement: Mechanism, Structure–Reactivity Relationship, and Parallels to Photoredox Catalysis

“…In recent decades, nonelectrochemical approaches toward enabling a transformation under milder conditions have been developed. These advancements include improved heat transfer by microwave irradiation − as well as decreasing the required temperature by using stoichiometric amounts of BF 3 ·OEt 2 or catalytic amounts of [Pd­( t Bu 3 P) 2 ] . More recently, it was shown that the O , S -rearrangement can be achieved at room temperature by irradiation with blue light in the presence of a pyrylium-based photoredox catalyst or by treatment with chemical oxidants. , Electrochemical catalysis, however, allows for additive-free reaction at room temperature, which was demonstrated by a synthetic study carried out in our laboratory (Scheme , bottom) …”