693255-81-1Relevant academic research and scientific papers
Cu(ii) catalysed chemoselective oxidative transformation of thiourea to thioamidoguanidine/2-aminobenzothiazole
Sahoo, Santosh K.,Khatun, Nilufa,Gogoi, Anupal,Deb, Arghya,Patel, Bhisma K.
, p. 438 - 446 (2013/04/10)
2-Haloaryl-sec-alkyl unsymmetrical thioureas (Tu) (halo = -F, -Cl) with a catalytic amount of Cu(ii) salt get oxidised in situ to their disulfide intermediates followed by an imine-disulfide rearrangement to give thioamidoguanidino (Tag) moieties at room temperature. During this process Cu(ii) gets reduced to Cu(i) and forms a complex with the Tag moiety from which Tag moiety can be isolated upon treatment with ammonia. However, when the same reaction was performed at an elevated temperature with a catalytic quantity of Cu(ii) salt, Tu bearing o-halogens (-F, -Cl) gave 2-aminobenzothiazoles via a dehalogenative heteroarylation path and not by the Hugerschoff path involving an electrophilic substitution reaction. For thioureas containing reactive ortho halogens (such as -Br, -I) the reaction proceeds at room temperature giving 2-aminobenzothiazoles via a dehalogenative path requiring a catalytic quantity of Cu(ii). No transformation of thiourea (Tu) to Tag was observed with Cu(i) salts suggesting the requirement of an oxidising Cu(ii) salt for this oxidative transformation. Mild reaction conditions, environmentally benign reagents and solvent, high yields, tolerance of various functional groups are some of the essential features of this methodology.
A ligand free copper(II) catalyst is as effective as a ligand assisted Pd(II) catalyst towards intramolecular C-S bond formation via C-H functionalization
Banerjee, Arghya,Santra, Sourav Kumar,Rout, Saroj Kumar,Patel, Bhisma K.
, p. 9096 - 9104 (2013/09/24)
Copper(I) catalysts are usually ineffective on the other hand Pd(II) catalysts are quite effective in promoting intramolecular sp2 C-H functionalization (C-S bond formation). Herein, we have developed a ligand assisted Pd(II) catalyzed C-S bond formation via C-H activation from arylthioureas leading to the formation of 2-aminobenzothiazoles for substrates bearing electron donating (EDG) groups in the aryl ring. However without the assistance of ligand this Pd(II) catalyzed reaction is quite unproductive particularly for thioureas possessing strongly electron donating groups in the aryl rings. Interestingly, the ligand free Cu(II) catalyzed oxidative cyclization of arylthioureas are equally effective both for arylthioureas possessing electron donating as well as electron withdrawing groups in the aryl rings.
