Nonreductive Desulfenylation of 3-Indolyl Sulfides. Improved Syntheses of 2-Substituted Indoles and 2-Indolyl Sulfides
摘要:
Desulfenylation of 3-indolyl sulfides to the corresponding 3-unsubstituted indoles is usually carried out under reductive conditions, thus accommodating only substituents which are resistant to reduction. We have developed a nonreductive procedure for removal of a sulfide at the 3-position of indoles, using trifluoroacetic acid in the presence of a thiol as trapping agent, which is compatible with a large array of functionalities on the indole ring. In addition, the desulfenylation occurs selectively at the 3-position of the indole, and sulfide groups at other positions of the molecule remain untouched. Thus, indole 2,3-bis-sulfides are selectively desulfenylated at the 3-position, affording 3-unsubstituted 2-indolyl sulfides. This methodology broadens the use of sulfide as a protecting group for the 3-position of indoles.
Nonreductive Desulfenylation of 3-Indolyl Sulfides. Improved Syntheses of 2-Substituted Indoles and 2-Indolyl Sulfides
摘要:
Desulfenylation of 3-indolyl sulfides to the corresponding 3-unsubstituted indoles is usually carried out under reductive conditions, thus accommodating only substituents which are resistant to reduction. We have developed a nonreductive procedure for removal of a sulfide at the 3-position of indoles, using trifluoroacetic acid in the presence of a thiol as trapping agent, which is compatible with a large array of functionalities on the indole ring. In addition, the desulfenylation occurs selectively at the 3-position of the indole, and sulfide groups at other positions of the molecule remain untouched. Thus, indole 2,3-bis-sulfides are selectively desulfenylated at the 3-position, affording 3-unsubstituted 2-indolyl sulfides. This methodology broadens the use of sulfide as a protecting group for the 3-position of indoles.
A method which avoids metal and halogen for the synthesis of 3-arylthioindoles from indoles and diaryl disulfides using ammonium persulfate in methanol has been presented. Moreover, double C–H sulfenylation of indoles at 2 and 3-positions has also been achieved using iodine and ammonium persulfate.
Copper-Catalyzed Multicomponent Reactions (MCRs) for Disulfenylation of Imidazo[1,2-<i>a</i>]pyridines Using Elemental Sulfur and Arylhalides and Intramolecular Cyclization of Haloimidazo[1,2-<i>a</i>]pyridines
Copper-catalyzed synthesis of disulfenylated imidazo[1,2-a]pyridines and indoles using elemental sulfur and haloarenes through one-pot, three component reaction by two C-S-C bond formations has been developed. The method has a broad substrate scope with a variety of substituted haloarenes. The conditions were also applied for the synthesis of benzothieno-imidazo[1,2-a]pyridines in excellent yields