Hai-Tao Zhu

Electrophile-driven regioselective synthesis of functionalized quinolines.

Highly substituted 3-iodoquinolines bearing different alkyl and aryl moieties can be synthesized in moderate to excellent yields (up to 99%) by 6-endo-dig iodocyclization of 2-tosylaminophenylprop-1-yn-3-ols with molecular iodine (I(2)) under mild conditions. The cyclization is highly regioselective and the resulting 3-iodoquinolines can be further functionalized by various coupling reactions.

Synthesis of five- and six-membered dihalogenated heterocyclic compounds by electrophile-triggered cyclization

Highly substituted dihalogenated dihydrofurans, dihydropyrroles, and dihydro-2H-pyrans bearing alkyl, vinyl, aryl, and heteroaryl moieties can be prepared in good to excellent yields (up to 99%) by allowing 1,4-butyne-diol, 4-aminobut-2-yn-1-ol, and pent-2-yne-1,5-diol derivatives to react with different electrophiles (I(2), IBr, and ICl) at room temperature. Both halogen atoms generated from electrophiles were used effectively. The resulting halides can be further exploited by using palladium-catalyzed coupling reactions. The presence of trace amount of water is essential for this electrophilic cyclization.

Electrophilic Carbocyclization of Aryl Propargylic Alcohols: A Facile Synthesis of Diiodinated Carbocycles and Heterocycles

Diiodinated carbocycles and oxygen heterocycles can be readily synthesized by electrophilic carbocyclization of aryl propargylic alcohols in moderate to good yields under mild conditions. The resulting diiodide can be further exploited by subsequent oxidizing and coupling reactions. Both the iodine anion and cation generated from I(2) are used effectively. The presence of a trace amount of water is essential for this electrophilic cyclization.

Novel Carbon−Carbon Bond Formation from Propargylic Alcohols and Olefin toward Five-Membered Heterocyclic Rings Catalyzed by AgSbF6

A mild and direct process for C-C bond formation from propargylic alcohols and olefin has been developed in the presence of a silver catalyst. In this reaction, trace amounts of water were necessary and allene alcohols 2 and 1,3-dienes 3 were obtained selectively.

Gold-Catalyzed Tandem [3,3]-Propargyl Ester Rearrangement Leading to (E)-1H-Inden-1-ones

An efficient method for the synthesis of (E)-1H-inden-1-ones using gold-catalyzed tandem [3,3]-propargyl ester rearrangement followed by Michael addition under mild reaction conditions has been developed. The resulting products are important frameworks found in numerous natural products and pharmaceutically active compounds, as well as being valuable intermediates in organic synthesis.

Highly regioselective synthesis of 1,3-diiodonaphthalene derivatives via a sequential cascade iodocyclization.

A novel and flexible sequentially cascade iodocyclization for the synthesis of highly substituted 1,3-diiodinated naphthalene derivatives in up to 99% yield under mild conditions is reported. The dihalogenated moiety can be readily introduced into the naphthalenes in a position that is usually not easily functionalized.

Electrophilic Carbocyclization of Hydroxylated Enynes

The electrophilic cyclization of nucleophiles, such as oxygen, nitrogen, sulfur, and carbon with alkynes was studied in detail by Barluenga, Larock, Kirsch, and others and has proved to be an effective method for the construction of cyclic compounds. However, electrophilic additions to allenes have often been considered to be synthetically less attractive because of to the lack of efficient control of the regio and stereoselectivity. Examples of electrophilic cyclization of allenes with nucleophiles for the construction of C X (C, N, and O) bonds include the cyclization of oxygen nucleophiles with allenes for the direct formation of a C O bond (Scheme 1a). Some important 4-iodofuran-2 ACHTUNGTRENNUNG(5H)-ones, most of which employ iodine to trigger the cyclization, have been developed using this method, while in an early report, Barluenga et al. have used IPy2BF4/HBF4 to promote the arylation of allenes at 90 8C (Scheme 1 b). However, the reaction conditions still need further improvement as the expensive IPy2BF4 electrophile is now used and low temperatures are still required. Simple olefins have not been used as internal carbon nucleophiles in this manner. In the context of our ongoing efforts to construct C X (C, N, and O) bonds by the use of alkynes with nucleophiles in domino reactions, we found that several transition metals, such as gold and platinum, show similar behavior with electrophiles as I . 7] The gold-catalyzed cycloisomerization of 1,n-enynes has become an effective way to construct various carbocyclic products. However, the electrophilic cyclization of simple hydroxylated enynes is a particularly challenging chemical transformation. According to our previous work, we envisioned that this type of propargyl alcohols A could eliminate the hydroxyl group to give the intermediate B in the presence of I2 (A–F, Scheme 1). Herein, we present preliminary results of a metal-free preparation of diiodocyclohexadienes and 2,3diiodobenzenes, in which the key cyclization step is the attack of unactivated olefins on allenes promoted by the iodonium ion at room temperature. Initially, we started by using the hydroxylated enyne 1 a (0.2 mmol) and I2 (1.2 equiv) in CH3NO2 at room temperature. To our delight, the desired products diiodocyclohexadiene (2 a and 3 a) were isolated in 70 % yield after 24 h (Table 1, entry 1). On increasing the amount of I2 [a] Dr. F. Yang, K.-G. Ji These authors contributed equally to this work. [b] Dr. F. Yang, K.-G. Ji, H.-T. Zhu, A. Shaukat, X.-Y. Liu, Prof. Dr. Y.-M. Liang State Key Laboratory of Applied Organic Chemistry Lanzhou University, Lanzhou 730000 (P.R. China) Fax: (+86) 931-8912582 E-mail : jikg08@gmail.com liangym@lzu.edu.cn Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201003759. Scheme 1. The domino process. E =electrophile, Py= pyridine.

Facile Synthesis of Carbazoles via a Tandem Iodocyclization with 1,2-Alkyl Migration and Aromatization

A strategy for the synthesis of iodocarbazoles through a tandem iodocyclization with migration and aromatization is presented. This sequential cascade process is concisely conducted at room temperature and in a short time. Moreover, the obtained halides can be further applied to palladium-catalyzed coupling reactions, which act as the important intermediates for building other valuable compounds.

Brønsted Acid Catalyzed Cyclization of Hydroxylated Enynes: A Concise Synthesis of Five‐Membered Heterocycles

A mild and direct pathway for the formation of five-membered heterocyclic compounds from hydroxylated enynes has been developed. In this reaction, hydroxylated enynes were selectively transformed into five-membered heterocyclic compounds 2, with an allene moiety at the 3-position, in the presence of F(3) CSO(3) H (0.1 mol %). When R(1) , R(2) =Ph, diphenylvinyl-2,3-dihydro-1H-pyrrole (2 y) was obtained. With HSbF(6) (5 mol %) as the catalyst, polycyclic skeletons 3 and 4 with adjacent stereocenters were obtained. When R(1) =H and R(2) =styrene, 1,3-dienyl-2,5-dihydro-1H-pyrrole (6 as) was formed. This Brønsted acid catalyzed domino process involves the formation of an allene carbocation intermediate, which can be readily trapped by olefins to give various novel five-membered heterocyclic skeletons.

Facile Synthesis of Halogenated Spiroketals via a Tandem Iodocyclization

A strategy for the synthesis of spiroketal compounds through a tandem iodocyclization of 1-(2-ethynylphenyl)-4-hydroxybut-2-yn-1-one derivatives is presented. This reaction could proceed under very mild conditions in a short time and avoid the use of expensive and toxic metal catalysts. Moreover, the resulting halides can be further exploited by subsequent palladium-catalyzed coupling reactions, which act as the important intermediates for building other valuable compounds.