Cycloadditions have become a mainstay of organic synthesis in the preparation of a wide host of natural products and medicines. photochemical 2+2 cycloadditions provide an especially valuable synthetic tool because of the efficiency with which several bonds are formed and because of the variety of ring systems that can be constructed by further manipulation of the initial polycyclic photoproducts. This proposal seeks to explore the scope of a newly discovered photoinduced cycloaddition of alkenes to excited triplet benzenes. The initial photoproducts are bicyclo (4.2.0)octa-2,4- dienes resulting from ortho 2+2 addition. These are converted thermally to cyclooctatrienes, which undergo photoisomerizaticn to bicyclo(4.2.0) octa-2,7-dienes. Thus the overall chemistry can lead either to eight-membered rings or to two different bicyclic structures that would lead to a variety of alternative structures. The compounds that have been studied already are (ortho - and para- butenoxy)phenyl ketones. Primary specific research aims are: 1) define the mechanism of the intramolecular reaction; 2) explore a wide variety of tethers other than -O-(CH2)2--; 3) explore how other substituents on the benzene ring affect the regioselectivity of addition; 4) explore the reactivity of variously substituted phenyl ketones in bimolecular addition; 5) determine the regioselectivity of bimolecular addition to the variously substituted benzenes; 6) explore triplet sensitized reactions of compounds without acyl groups so as to broaden the reaction's usefulness; 7) determine the reactivity of heteroaromatics, which would lead to various heterocyclic products; 8) illustrate the reaction's usefulness by preparing several ring systems of current synthetic interest. The overall aims of the research are 1) to define how well this photochemistry may complement the cycloaddition of alkenes to cycloalkenones and to singlet excited benzenes as synthetic methodology; and 2) to develop a much better understanding of the reactivity of excited triplet benzenes.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM039821-03
Application #
3297045
Study Section
Medicinal Chemistry Study Section (MCHA)
Project Start
1989-07-01
Project End
1992-06-30
Budget Start
1991-07-01
Budget End
1992-06-30
Support Year
3
Fiscal Year
1991
Total Cost
Indirect Cost
Name
Michigan State University
Department
Type
Schools of Arts and Sciences
DUNS #
193247145
City
East Lansing
State
MI
Country
United States
Zip Code
48824
Nadeau, J H; Herrmann, B; Bucan, M et al. (1991) Genetic maps of mouse chromosome 17 including 12 new anonymous DNA loci and 25 anchor loci. Genomics 9:78-89