Zitao Wang

Efficient one-pot synthesis of 2,3-dihydropyrimidinthiones via multicomponent coupling of terminal alkynes, elemental sulfur, and carbodiimides.

An organolithium-promoted multicomponent reaction (MCR) involving readily available terminal alkynes, elemental sulfur, and carbodiimides has been achieved for the first time. This MCR offers an atom-economic route to 2,3-dihydropyrimidinthiones which are difficult to access by other means via an interesting and useful C=N double bond cleavage and an sp(3) C-H bond functionalization of carbodiimides.

Procedure-Controlled Selective Synthesis of 5-Acyl-2-iminothiazolines and their Selenium and Tellurium Derivatives by Convergent Tandem Annulation†

Concise and selective: the procedure-controlled synthesis of the title compounds has been achieved for the first time by an organolithium-promoted convergent tandem annulation involving readily available terminal alkynes, chalcogen elements (S, Se, and Te), carbodiimides, and acid chlorides. A novel 1,5-acyl migration is considered to be essential for this useful transformation.

Iterative Dianion Relay Along the Ring: Formation of gem-Bis(trimethylsilyl) Cyclopentenones from 2,5-Bis(trimethylsilyl) Oxy-cyclopentadienyl Dianions and Acid Chlorides

Anionic migration of silyl groups has become one of the most useful protocols for synthetic chemistry. The intramolecular 1,n-anionic migration of a silyl group from a carbon atom to an oxygen atom is generally referred to as Brook rearrangement (Scheme 1) and the reverse process (from an oxygen atom to a carbon atom) is called retroBrook rearrangement (or West rearrangement). Both the Brook rearrangement and the retro-Brook rearrangement are currently widely applied in organic synthesis. As illustrated in Scheme 1, a recent yet very useful strategy applying anionic migrations of silyl groups is the anion relay chemistry (ARC) developed by Smith III et al. The ARC, a multi-component linchpin protocol, has been demonstrated to be useful for high-efficient and facile synthesis of structurally complex scaffolds. To further apply to synthetic chemistry the useful protocol based on the anionic migration of silyl groups, the design and development of new linchpins is currently of great demand and represents a great challenge. In recent years, we have demonstrated that the reaction of 1,4-dilithio-1,3-butadienes 1 with CO leads to the formation of substituted oxy-cyclopentadienyl dianion intermediates 2 (OCp dianions; Cp =cyclopentadienyl). Because of the concomitance of the Cp anion, the exocyclic oxyanion, and those multi-reactive sites, the OCp dianions 2 are structurally very unique and can be used for novel reaction chemistry. During the course of our continuous study on their reaction chemistry, we realized that those OCp diACHTUNGTRENNUNGanions substituted with trimethylsilyl groups could be used as a new type of dianionic relay linchpins. Iterative anion relay, in which one silyl group was shifted twice along the Cp ring with the exocyclic oxyanion as the posthouse, was observed the first time in anionic migration of silyl groups (Scheme 1). Interesting and otherwise unavailable compounds have been thus generated. Herein, we report our preliminary results. 1,4-Dilithio-1,4-bis(trimethylsilyl)-1,3-butadienes (dilithio reagents) 1 can be readily generated in quantitative yields from their corresponding 1,4-diiodobutadienes and tBuLi. Treatment of dilithio reagents 1 with CO led to the formation of OCp dianions 2. When the reaction mixture containing 2 a in diethyl ether was further treated with two equivalents of ArCOCl possessing electron-donating groups on Ar, such as 4-methylbenzoyl chloride, a double-acylation product was obtained. However, surprisingly, when one equivalent of PhCOCl was used, the 3-cyclopentenone derivative 5 aa containing a stable enol moiety was obtained in 74 % [a] H. Li, Dr. L. Liu, Z. Wang, F. Zhao, S. Zhang, Prof. Dr. W.-X. Zhang, Prof. Dr. Z. Xi Beijing National Laboratory for Molecular Sciences (BNLMS) Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, College of Chemistry Peking University, Beijing 100871 (P.R. China) Fax: (+86) 10-62751708 E-mail : zfxi@pku.edu.cn [b] Prof. Dr. Z. Xi State Key Laboratory of Organometallic Chemistry SIOC, CAS Shanghai 200032 (P.R. China) Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201100830. Scheme 1. Modes of anionic migration of silyl groups. ASG=anion stabilizing group, LP = linchpin.

The First Lutetacyclopentadienes: Synthesis, Structure, and Diversified Insertion/CH Activation Reactivity

The first well-defined lutetacyclopentadienes are synthesised from pentamethylcyclopentadienyl lithium (Cp*Li), 1,4-dilithio-1,3-butadienes, and LuCl3. The lutetacyclopentadiene shows excellent reactivity towards some small molecules, such as pivalaldehyde, Se, carbon dioxide, and isonitrile to efficiently construct 3-, 5-, 7-, 8-, and 9-membered rare-earth metallacycles. Both monoinsertion and double-insertion of two Lu-Csp2 bonds are observed. Specially, the reaction between lutetacyclopentadiene and isonitrile afforded [3,5,5]-fused metallacycles. The distinguished reactivity can be attributed to the highly ionic character and the cooperative reactivity of two Lu-Csp2 bonds.

Mechanistic Study on the Cleavage and Reorganization of C(sp3)H and CN Bonds in Carbodiimides: Synthesis of 1,2‐Dihydrothiopyrimidines and 2,3‐Dihydropyrimidinthiones through Four‐Component Coupling

This study sheds light on the cleavage and reorganization of C(sp(3))-H and C=N bonds of carbodiimides in a three-component reaction of terminal alkynes, sulfur, and carbodiimides by a combination of methods including 1) isolation and X-ray analysis of six-membered-ring lithium species 2-S, 2) trapping of the oxygen-analogues (B-O and D-O) of both four-membered-ring intermediate B-S and ring-opening intermediate D-S, 3) deuterium labeling studies, and 4) theoretical studies. These results show that 1) the reaction rate-determining step is [2+2] cycloaddition, 2) the C=N bond cleavage takes place before C(sp(3))-H bond cleavage, 3) the hydrogen attached to C6 in 2-S originates from the carbodiimide, and 4) three types of new aza-heterocycles, such as 1,2-dihydrothiopyrimidines, N-acyl 2,3-dihydropyrimidinthiones, and 1,2-dihydropyrimidinamino acids are constructed efficiently based on 2-S. All results strongly support the idea that the reaction proceeds through [2+2] cycloaddition/4π electrocyclic ring-opening/1,5-H shift/6π electrocyclic ring-closing as key steps. The research strategy on the synthesis, isolation, and reactivity investigation of important intermediates in metal-mediated reactions not only helps achieve an in-depth understanding of reaction mechanisms but also leads to the discovery of new synthetically useful reactions based on the important intermediates.

Construction of octaalkyl-substituted and decasubstituted all-cis-octatetraenes via linear dimerization of 1,4-dicopper-1,3-butadienes and subsequent cross-coupling with halides.

Lithium iodide-assisted linear dimerization of 1,4-dicopper-1,3-butadienes and subsequent Pd-catalyzed cross-coupling reaction with halides provide an efficient way to construct octaalkyl-substituted and decasubstituted all-cis octatetraenes.

CCDC 808715: Experimental Crystal Structure Determination

Related Article: Wen-Xiong Zhang, Zitao Wang, M.Nishiura, Zhenfeng Xi, Zhaomin Hou|2011|J.Am.Chem.Soc.|133|5712|doi:10.1021/ja200540b