Efficient Syntheses of 2-Functionalized Thiophenes, Cyclopent[b]thiophenes, and Polysubstituted Benzo[b]thiophenes from 2-(Benzotriazol-1-ylmethyl)thiophenes
摘要:
Diverse 2-(functionalized-alkyl)- and 2-alkenylthiophenes 2a,b, 4a,b, and 6a-d are prepared via the side chain elaboration of 2-(benzotriazol-1-ylmethyl)thiophenes 3a,b, themselves readily available from the condensation of 1-(hydroxymethyl)benzotriazole with thiophenes 1a,b. Treatment of 2-(benzotriazol-1-ylmethyl)thiophenes 3b and 5gj with styrenes in the presence of zinc bromide results in formal [3 + 2] cycloaddition to give in good yields substituted cyclopent[b]thiophenes 16a/17a, 16b/17b, and 18. Lithiation and 1,4-addition to a variety of alpha,beta-unsaturated ketones and aldehydes, and subsequent acid-catalyzed intramolecular cyclization followed by debenzotriazolylation-dehydration converts 3 and 5 to a range of polysubstituted benzo[b]thiophenes 19a-d and 25a-e in moderate to excellent yields. NOE difference spectroscopy and NMR H-1-C-13 long-range correlation support structures of types 19 and 25 and exclude those of type 26, thus confirming the cyclization pathway.
The iridium-catalyzed highly chemoselective hydrogenation of amides to amines has been developed. Using a well-defined iridium catalyst bearing a P(O)C(O)P pincer ligand combined with B(C6F5)3, the C–O cleavage products are formed undermildreactionconditions. The reaction provides a new method for the preparation of amines from amides in good yield with high selectivity.
已经开发了铱催化的酰胺高度化学选择性氢化成胺的方法。使用带有P(O)C(O)P钳形配体与B(C 6 F 5)3结合的明确定义的铱催化剂,在温和的反应条件下可形成C–O裂解产物。该反应提供了一种以高收率和高选择性从酰胺制备胺的新方法。
Boron Lewis Acid Promoted Ruthenium-Catalyzed Hydrogenation of Amides: An Efficient Approach to Secondary Amines
作者:Ming-Lei Yuan、Jian-Hua Xie、Qi-Lin Zhou
DOI:10.1002/cctc.201600635
日期:2016.10.6
The hydrogenation of amides to amines has been developed by using the catalyst [Ru(H)2(CO)(Triphos)] (Triphos=1,1,1‐tri(diphenylphosphinomethyl)ethane) and catalytic boron Lewis acids such as B(C6F5)3 or BF3⋅Et2O as additives. The reaction provides an efficient method for the preparation of secondary amines from amides in good yields with high selectivity.
A process for the activation of carboxylic acids which is useful for the subsequent conversion of said carboxylic acids into their corresponding amides or esters, based on reacting a 2-oxazolidinone with phosphorus pentachloride and subsequent addition of a salt of the carboxylic acid to be activated.
N-alkylation of amines by using secondary amides as the alkyl source was developed. A versatile type of carboxamide functioned as an N-alkylation reagent in the presence of an indium(III) catalyst and a hydrosilane to provide alkylated tertiary aminesefficiently. This amide-based catalytic N-alkylation strategy is considered to be a highly useful protocol to access unsymmetrical tertiary amines.
isocyanates at the benzylic position upon irradiation with visiblelight in the presence of an iridium photoredox catalyst, a bromide anion, and a nickel catalyst, producing N-substituted α-aryl amides. An analogous carbamoylation reaction of aliphatic C–H bonds of alkanes took place when UV light and a diaryl ketone were used instead of visiblelight and the iridium complex. The present reaction offers