Yu-Xin Zhang

Gold Catalyzed Diastereoselective Cascade Allylation/Enyne Cycloisomerization to Construct Densely Functionalized Oxygen Hetereocycles

A new tandem allylation/enyne cycloisomerization reaction was developed to construct densely functionalized oxygen heterocycles with high diastereoselectivities from the intermolecular reaction of allylic acetates with propargylic alcohols via gold catalysis. Terminal and nonterminal propargylic alcohols take different reaction routes either to provide 3-oxa-bicyclo[4.1.0]hept-4-ene derivatives 5 or to give endocyclic rearrangement products 7 and alkoxycyclization adducts 8. Cyclopropanes stereochemistry was mainly determined by allylic substituents.

Composite attitude control for flexible spacecraft with simultaneous disturbance attenuation and rejection performance

In this paper, a composite attitude control approach for orbiting spacecraft with rigid central hubs and flexible appendages is presented. The established attitude control model consists of the vibration modes excited by the rigid body, the space environment disturbances, the measurement noises, and the model uncertainty. The model is formulated into a dynamic system with two types of disturbance inputs. A composite control law with the simultaneous disturbance attenuation and rejection performance is presented for the flexible spacecraft system subject to multiple disturbances. The disturbance-observer-based control is designed for feedforward compensation of the elastic vibration. The H∞ state-feedback controller is designed to perform the robust attitude control in the presence of the space environment disturbances, measurement noises, and the model uncertainty. Numerical simulations show that the performance of the attitude control systems can be improved by combining the disturbance observer with H∞ state-feedback control.

Gold Catalyzed Carbocyclization of Dienyl Acetates to Construct Mutifunctionalized 3-Vinyl Cyclohexanol Derivatives

A convenient new method was developed to construct six-membered 3-vinylcyclohexanols (and piperidine products) and 6-oxabicyclo[3.2.1]octan-7-one derivatives with high diastereoselectivities from 1,6-dienyl acetates via gold catalysis. The reaction proceeded through the nucleophilic addition of the alkenes onto the allylic cation group via a 6-endo-trig process. The substrates structure affected the configuration orientation of the allylic cation group in a boatlike transition state, which afforded either the trans-cyclohexanols or cis-piperidine derivatives.

Synthesis and Structural Determination of Two Types of Novel Cyclic Carbonates

Two types of novel cyclic carbonates, including 7-benzylidene-4,6-oxa-5- carbonyl–spiro[2,4] heptane 3a and 7-phenyl-4,6-oxa-5-carbonyl–spiro [2,5] 7-octene 4a, were readily synthesized from 1-alkynyl cyclopropyl tButyl carbonate by using AuCl(PPh3)/ Ag(OTf) as catalysts. The structure of compound 3a was identified to be a 5-member cyclic carbonate by X-ray crystallographic analysis, of which the unit cell has monoclinic P2(1)/c symmetry with the cell parameters a = 7.0543(14) Å, b = 10.556(2) Å, c = 13.066(3) Å, and Z = 4. Therefore, the structure of compound 4a can be deduced to be a six membered cyclopropane-containing cyclic carbonate.

CCDC 776682: Experimental Crystal Structure Determination

Related Article: Li-Li Zhu, Ya-Hui Wang, Yu-Xin Zhang, Xiao-Xiao Li, Heng Liu, Zili Chen|2011|J.Org.Chem.|76|441|doi:10.1021/jo1018014

An Efficient Method to Construct 2-vinylidenyl Cyclobutanone Derivatives and its Structural Determination

2-Vinylidenyl cyclobutanone derivatives 5 can be readily synthesized from the dialkynyl cyclopropanols 4 through a consecutive process of 1,6-diynes carbocyclization and ring enlargement of cyclopropnaol unit by using AuCl(PPh 3 )/AgPF 6 as catalyst in DCE at rt. The structure of compound 5a was identified to a 2-vinylidenyl cyclobutanone by X-ray crystallographic analysis. The unit cell has monoclinic P2(1)/c symmetry with the cell parameters a = 10.919(2) Å, b = 17.508(4) Å, c = 7.9219(16) Å, and Z = 4.