Copper-Catalyzed Oxidative Amination of Benzoxazoles via C−H and C−N Bond Activation: A New Strategy for Using Tertiary Amines as Nitrogen Group Sources
method for oxidative amination of azoles with tertiary aminesviacopper-catalyzed C−H and C−Nbond activation has been developed. This protocol can be performed in the absence of external base and only requires atmospheric oxygen as oxidant. The catalyst system is very simple and efficient, which opens a new way for using tertiary amines as nitrogen group sources for C−Nbondformation reactions.
The unprecedented reaction of tertiary amines with 2(3H)-benzoxazolones has been investigated. In the presence of the Ph3P–I2 reagent system, the reaction of both acyclic and cyclic aliphatic tertiary amines led to the formation of 2-N,N-dialkylaminobenzoxazoles with the selective cleavage of an alkyl group. Especially, N-(2-iodoethyl)piperazinyl derivatives were rapidly produced in good yields when
已研究了叔胺与2(3 H)-苯并恶唑酮的空前反应。在Ph 3 P–I 2试剂体系的存在下,无环和环状脂族叔胺的反应均导致2- N,N-二烷基氨基苯并恶唑的形成,并选择性地裂解了烷基。特别地,当使用DABCO作为氮源时,N-(2-碘乙基)哌嗪基衍生物以高收率快速生产。仅在底物的亲核性超过胺的亲核性的情况下,苯并恶唑酮的竞争性自缩合才优先进行。31 P 11 H-NMR研究表明涉及芳氧基phosph中间体和/或可能的2-碘苯并恶唑,其激活苯并恶唑酮的C-2位朝亲核芳族取代。
Utilization of carbon disulfide as a powerful building block for the synthesis of 2-aminobenzoxazoles
This protocol describes a novel, mild and convenient route to afford 2-aminobenzoxazoles in high yields, and represents a significant advance towards an environmentally friendly strategy. Aliphatic amines are made to react with carbon disulfide to provide intermediate dithiocarbamates (DTC), which in the presence of 2-aminophenol, subsequently undergo successive intermolecular nucleophilic attack and desulfurization to produce 2-aminobenzoxazoles within 3 h.
Metal-free synthesis of 2-aminobenzoxazoles using hypervalent iodine reagent
作者:Yogesh S. Wagh、Neelam J. Tiwari、Bhalchandra M. Bhanage
DOI:10.1016/j.tetlet.2012.12.127
日期:2013.3
A facile, simple, mild, and metal-free protocol for the synthesis of 2-aminobenzoxazoles has been developed via C–H bond amination of benzoxazoles with amines through a ring-opening and subsequent ring-closure approach. The reaction was performed in two steps wherein nucleophilic addition of amines across benzoxazoles takes place in the absence of any reagent or catalyst under solvent-free condition
dithiocarbamates and tetramethylthiuram disulfide (TMTD), respectively. With the promotion of NaH/CuI, the reaction of o-aminophenols with dithiocarbamates gave 2-aminobenzoxazoles with good yield (70–92%) in one pot manner, and 2-mercaptobenzoxazoles were synthesized (yield: 55–80%) in the presence of K2CO3 by treating o-aminophenols with tetramethylthiuram disulfide (TMTD). The feature of this method