Stereoselective Synthesis of (Z)-2,3-Dihydro-3-(arylmethylene)benzofurans via the Palladium Catalyzed Insertion and Cross Coupling Reaction of 1-Iodo-2-(2-propynyloxy)benzene and Arylzinc Chloride
摘要:
The title compound was prepared in fair to good yields from 1-iodo-2-(2-propynyloxy)benzene and arylzinc chloride via tandem insertion and cross coupling reaction catalyzed by pertinent palladium catalyst, such as palladium acetate and triphenylphosphine.
Carbonickelations of alkynes and functionalization of the resulting vinylnickel moiety have been performed efficiently in a nickel‐catalyzed domino cyclization–condensation process. This reaction, which does not require the preparation of any other organometallic reagent, proceeds only by exo‐dig cyclization. This convenient and mild method constitutes a one‐pot synthesis of substituted dihydrobenzofurans
Reaction of Ni(0) in the presence of iodoarylethers 1 leads, after syn intramolecular carbonickelation of the triple bond, to nucleophilic vinylnickels which can be trapped, in a tandem process, by various electrophiles introduced at the onset of the reaction.
The intramolecularcarbolithiation of a series of propargylic ethers has been performed to evaluate the influence of the terminal substituent on the efficiency and the stereochemical outcome of the cyclization. Our results show that only 5-exo-dig cyclizations are observed, and dihydrobenzofurans are obtained exclusively. Depending on the nature of the terminal substituent, two cases can be considered
已经进行了一系列炔丙醚的分子内碳锂化,以评估末端取代基对环化效率和立体化学结果的影响。我们的结果表明,仅观察到 5-exo-dig 环化,并且仅获得了二氢苯并呋喃。根据末端取代基的性质,可以考虑两种情况。如果炔烃碳原子携带的末端取代基本身是碳原子,则只要末端炔丙基位置带有配位元素并且至少是二取代的,就可以发生环化。当环化发生时,它遵循反碳石化途径,从而导致环外双键的 E 异构体。仅在一种情况下(Ph)是回收的所得烯烃的E和Z异构体的混合物。如果调节环化条件,炔烃直接被 S 或 Si 取代,也可以发生环化。在三甲基甲硅烷基取代基的情况下,观察到顺式碳锂化。如果双键被恢复,在大多数情况下,在环外位置,产物可以直接芳构化为 SPh 取代的底物 24。此外,在后两种情况下,当进行乙烯基锂中间体的烷基化时,双键的异构化似乎是瞬间的。
Iridium-Catalyzed Intramolecular Methoxy C−H Addition to Carbon-Carbon Triple Bonds: Direct Synthesis of 3-Substituted Benzofurans from <i>o</i>
-Methoxyphenylalkynes
Catalytic hydroalkylation of an alkyne with methyl ether was accomplished. Intramolecular addition of the C−H bond of a methoxy group in 1‐methoxy‐2‐(arylethynyl)benzenes across a carbon–carbontriple bond took place efficiently either in toluene at 110 °C or in p‐xylene at 135 °C in the presence of an iridium catalyst. The initial 5‐exo cyclization products underwent double‐bond migration during the
Unique selectivity, hitherto not observable in ordinary radical and ionic reactions, is achieved with the bowl-shaped tris(2,6-diphenylbenzyl)tin hydride (TDTH; see structure), which has been successfully utilized as a new reducingagent.