Free radical macrocyclization

Conference · Mon Sep 01 04:00:00 EDT 1986 · Am. Chem. Soc., Div. Pet. Chem., Gen. Pap., Prepr.; (United States)

OSTI ID:6867762

Porter, N A; Magnin, D R; Wright, B T

Free radical reactions have been used increasingly in recent years for the synthesis of organic molecules. The development of radical synthesis is primarily the result of mechanistic studies of the past forty years that have identified the important pathways available and have provided detailed reactivity guidelines for such reactions. Mechanistic studies provided a framework for understanding free radical cyclization, for example, and this approach has been extensively utilized for the construction of natural products in subsequent elegant investigations. The use of radical cyclization has been limited primarily to the construction of five- and six-membered rings and has not been used for larger ring systems. In fact, the rate of cyclization decreases from 2 x 10/sup 5/ s/sup -1/ for 5-exo cyclization (5-hexenyl at 25/sup 0/C) to <70 s/sup -1/ for the corresponding 7-exo reaction. It occurred to the authors that radical cyclization might prove to be possible for larger rings if they chose substrates that gave consideration to steric and polar effects in the cyclization reaction. Carbon radicals of nucleophilic and electron-withdrawing substituents activate alkenes toward addition of such radicals. Furthermore, substrates that minimize steric effects in the cyclization transition state are preferred, since this can be a dominant reactor in addition reactions. They report the results of the studies with several substrates for radical macrocyclization. The reaction proves useful with yields as high as 75-80% for some substrates.

• Research Organization: Dept. of Chemistry, Duke Univ., Durham, NC
• OSTI ID: 6867762
• Report Number(s): CONF-860911-
• Conference Information: Journal Name: Am. Chem. Soc., Div. Pet. Chem., Gen. Pap., Prepr.; (United States) Journal Volume: 31:3
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical &amp; Physicochemical Properties
ALKENES
CARBON COMPOUNDS
CHARGED-PARTICLE REACTIONS
CHEMICAL PREPARATION
CHEMICAL REACTION KINETICS
CHEMICAL REACTION YIELD
CHEMICAL REACTIONS
DEHYDROCYCLIZATION
ELECTRON REACTIONS
HYDROCARBONS
KINETICS
LEPTON REACTIONS
MEDIUM TEMPERATURE
NUCLEAR REACTIONS
ORGANIC COMPOUNDS
RADICALS
REACTION KINETICS
STEREOCHEMISTRY
SUBSTRATES
SYNTHESIS
YIELDS