Catalytic Desulfurization of Dibenzothiophene and 4,6-Dimethyldibenzothiophene with Nickel Compounds

Abstract

Catalytic amounts of the compounds [(dippe)- NiH] 2 (1), [(dcpe)NiH] 2 (2), and [Ni(PEt 3 ) 4 ] (3) (1-0.1 mol %) with alkyl Grignard reagents promoted the desulfurization of dibenzothiophene, 4-methyldibenzothiophene, and 4,6-dimethyldibenzothiophene, to produce the corresponding biphenyls (90-100%) in toluene or mixtures of biphenyls and thiols favored in THF. Also, the thianickelacycle [(dippe)Ni(η 2 -C,S-C 12 H 8 )] ( 4) was used as a catalyst precursor to test its participation as an active intermediary in the catalytic cycle.

α‐Arylation of Ketimines with Aryl Sulfides at a Low Palladium Catalyst Loading

“…[9f,g] promoted the arylation reaction, though the reaction was less efficient in each case (entries [8][9][10]. Theyield of 3aa was dramatically improved to 81 %b yi ncreasing the amount of LiN(SiMe 3 ) 2 to two equivalents (entry 11) to compensate for deprotonation of the initially formed aarylated ketimine product of higher acidity.S urprisingly,t he catalyst loading could be decreased to 0.5 mol %w ithout losing the efficiency( entry 12), an exceptionally low homogeneous catalyst loading for CÀSb ond cleavage.Afurther decrease of the catalyst loading to 0.1 mol %r esulted in amarked decrease in yield to 49 %(entry 13).…”

“…[5] Even worse,m uch more poisonous thiolate anions are inevitably formed as byproducts.K nown catalytic CÀS bond-cleavage reactions, [6] including ours, [7] required large amounts of catalysts (over 2mol %, but generally 5-20 mol %) [8] and/or stoichiometric amounts of transitionmetal salts (typically thiophilic copper salts). By considering that CÀSb onds exist widely in organic feedstock and synthetic intermediates,t he development of efficient transformations of C À Sbonds with aminimal amount of acatalyst has been an important challenge both in academia and in industry.…”

α‐Arylation of Ketimines with Aryl Sulfides at a Low Palladium Catalyst Loading

“…[5] Even worse,m uch more poisonous thiolate anions are inevitably formed as byproducts.K nown catalytic CÀS bond-cleavage reactions, [6] including ours, [7] required large amounts of catalysts (over 2mol %, but generally 5-20 mol %) [8] and/or stoichiometric amounts of transitionmetal salts (typically thiophilic copper salts). [5] Even worse,m uch more poisonous thiolate anions are inevitably formed as byproducts.K nown catalytic CÀS bond-cleavage reactions, [6] including ours, [7] required large amounts of catalysts (over 2mol %, but generally 5-20 mol %) [8] and/or stoichiometric amounts of transitionmetal salts (typically thiophilic copper salts).…”

“…Either electrondonating or -withdrawing groups at the para position of aryl sulfides had only little influence on the reaction efficiencyto afford the corresponding products 3da-la in moderate to good yields (entries [3][4][5][6][7][8][9][10][11]. Sterically hindered o-tolyl sulfide 1b afforded the desired product 3ba in 76 %y ield, albeit in the presence of 1mol %o f SingaCycle-A1 (still al ow catalyst loading).…”

“…Compared to aryl halides and phenol derivatives,a ryl sulfides have been underdeveloped as aryl electrophiles in catalytic transformations because they are poisonous to transition-metal catalysts and they have unpleasant smells. [5] Even worse,m uch more poisonous thiolate anions are inevitably formed as byproducts.K nown catalytic CÀS bond-cleavage reactions, [6] including ours, [7] required large amounts of catalysts (over 2mol %, but generally 5-20 mol %) [8] and/or stoichiometric amounts of transitionmetal salts (typically thiophilic copper salts). By considering that CÀSb onds exist widely in organic feedstock and synthetic intermediates,t he development of efficient transformations of C À Sbonds with aminimal amount of acatalyst has been an important challenge both in academia and in industry.…”