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An K.,Xiamen University | Zhu J.,Xiamen University | Zhu J.,Peking University Shenzhen Graduate School
European Journal of Organic Chemistry | Year: 2014

Aromaticity, one of the most important concepts in chemistry, has attracted considerable interest from both experimentalists and theoreticians. According to Baird's rule, triplet annulenes with 4n π electrons are aromatic. However, the approach to evaluate the magnitude of the triplet aromaticity is less developed. Herein we apply the indene-isoindene isomerization stabilization energy (ISE) method to evaluate the aromaticity in the triplet state. The reliability of this approach can be demonstrated by the strong correlation of these indene-isoindene ISE values with nucleus-independent chemical shifts [NICS(1)zz] as well as methyl-methylene ISE values. Large [4n]annulenes have the tendency to be planar to achieve aromaticity in the T1 state. Steric effects play an important role in the stabilities of large [4n]annulene isomers. Triplet aromaticity has been evaluated by applying the indene-isoindene isomerization stabilization energy (ISE) method. The reliability of this approach can be demonstrated by the strong correlation of ISE values with NICS(1)zz as well as the previous methyl-methylene ISE values. Our results verify Baird's rule: that triplet annulenes with 4n π-electrons are aromatic. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Meng L.,Wuhan University | Wu K.,Wuhan University | Liu C.,Wuhan University | Lei A.,Wuhan University | Lei A.,Peking University Shenzhen Graduate School
Chemical Communications | Year: 2013

The first palladium-catalysed aerobic oxidative intramolecular alkenylation of Csp3-H bonds was described. The reaction conditions were mild and molecular oxygen was used as the terminal oxidant. Kinetic studies showed that the Csp3-H metallation step was a slow step. © 2013 The Royal Society of Chemistry. Source

Han J.-C.,South University of Science and Technology of China | Li F.,Peking University Shenzhen Graduate School | Li C.-C.,South University of Science and Technology of China | Li C.-C.,Peking University Shenzhen Graduate School
Journal of the American Chemical Society | Year: 2014

A new method has been developed for the concise and asymmetric synthesis of seven humulanolides in 5-7 steps without the need for protecting groups. Notably, the challenging 11-membered ring and bridged butenolide moieties in asteriscunolide D and 6,7,9,10-tetrahydroasteriscunolide were introduced in one step using a ring-opening/ring-closing metathesis cascade reaction. Asteriscunolide D was used as a versatile synthetic precursor to prepare asteriscunolides A-C via a photoinduced isomerization reaction, asteriscanolide via a unique transannular Michael reaction, and 6,7,9,10-tetradehydroasteriscanolide via a transannular Morita-Baylis-Hillman-type reaction. The unique bicyclo[6.3.0]undecane core was introduced diastereoselectively. © 2014 American Chemical Society. Source

Zhang Y.,Peking University Shenzhen Graduate School | Luo T.,CAS Beijing National Laboratory for Molecular | Yang Z.,Peking University Shenzhen Graduate School | Yang Z.,CAS Beijing National Laboratory for Molecular
Natural Product Reports | Year: 2014

Novel organic reactions drive the advance of chemical synthesis in the same way that enabling technologies drive new scientific discoveries. One area of organic methodology that has undergone significant growth during the last decade is that of homogeneous gold-catalyzed transformations. This trend has been further enhanced by the employment of gold catalysis on a routine basis to accomplish the total synthesis of natural products. In particular, the superior π acidity of the cationic gold complex for the activation of alkynes and allenes towards nucleophilic addition has significantly enriched the toolkit of transformations available to the total synthesis community, and inspired a new era of creativity in terms of the strategic disconnection of target compounds during their retrosynthetic analysis. Instead of simply supplementing the many existing reviews of gold catalysis, this review has been organized from the perspective of synthetic target families, with particular emphasis on the use of gold-catalyzed transformations during the late stages of syntheses involving complicated substrates, and cascade reactions that significantly increase molecular complexity. This journal is © the Partner Organisations 2014. Source

Wang C.,Peking University Shenzhen Graduate School | Huang Y.,Peking University Shenzhen Graduate School
Synlett | Year: 2013

The need to use a static directing group represents a major limitation for the emerging field of ortho-selective C-H activation and functionalization. Chemistry was recently developed that allowed partial removal or minor transformations for certain directing groups. Our recent work demonstrated that triazenes were a class of excellent directing groups for C-H activation/functionalization, and subsequent chemical manipulations generated key compounds with synthetic versatility. © Georg Thieme Verlag Stuttgart · New York. Source

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