Biomaterial Database

Alkene distortion energies and torsional effects control reactivities, and stereoselectivities of azide cycloadditions to norbornene and substituted norbornenes. 2013

Steven A Lopez, and K N Houk

Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, United States.

The transition structures for 1,3-dipolar cycloadditions of phenyl azide to norbornene derivatives were located with quantum mechanical methods. Calculations were carried out with M06-2X/6-311G(d,p) and SCS-MP2/6-311G(d,p)//M06-2X/6-311G(d,p) methods. The calculated activation barriers strongly correlate with transition state distortion energies (ΔE(d‡)) but not with the reaction energies. Strain-promoted reactions are accelerated because it is easy to distort the strained reactants to a pyramidalized transition state geometry; a correlation of cycloaddition rates with substrate distortion was found for the bicyclic and tricyclic alkenes studied here. The stereoselectivities of reactions of norbornene derivatives are controlled primarily by torsional effects that also influence alkene pyramidalization. These reactions are distortion-accelerated.

UI	MeSH Term	Description	Entries
D008956	Models, Chemical	Theoretical representations that simulate the behavior or activity of chemical processes or phenomena; includes the use of mathematical equations, computers, and other electronic equipment.	Chemical Models,Chemical Model,Model, Chemical
D009636	Norbornanes	Compounds that include or are derivatives of norbornane(bicyclo[2.2.1]heptane).	Norbornane Derivatives,Norbornene Derivatives,Norbornenes,Norcamphanes,Derivatives, Norbornane,Derivatives, Norbornene
D011789	Quantum Theory	The theory that the radiation and absorption of energy take place in definite quantities called quanta (E) which vary in size and are defined by the equation E	Quantum Theories,Theories, Quantum,Theory, Quantum
D000475	Alkenes	Unsaturated hydrocarbons of the type Cn-H2n, indicated by the suffix -ene. (Grant & Hackh's Chemical Dictionary, 5th ed, p408)	Alkene,Olefin,Olefins,Pentene,Pentenes
D001386	Azides	Organic or inorganic compounds that contain the -N3 group.	Azide
D013237	Stereoisomerism	The phenomenon whereby compounds whose molecules have the same number and kind of atoms and the same atomic arrangement, but differ in their spatial relationships. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 5th ed)	Molecular Stereochemistry,Stereoisomers,Stereochemistry, Molecular,Stereoisomer
D013816	Thermodynamics	A rigorously mathematical analysis of energy relationships (heat, work, temperature, and equilibrium). It describes systems whose states are determined by thermal parameters, such as temperature, in addition to mechanical and electromagnetic parameters. (From Hawley's Condensed Chemical Dictionary, 12th ed)	Thermodynamic