THE COUPLING OF (E)- AND (Z)-2-IODO-1-SULFONYLALKENES AND ALPHA-HALOSULFONES WITH MONOCOPPER(I) REAGENTS
Abstract
The coupling of organocopper reagents with (E)- and (Z)-2-iodo-1-sulfonylalkenes was investigated as a means of preparing vinyl sulfones with known stereochemistry. The starting (E)- and (Z)-2-iodo-1-sulfonylalkenes were prepared by known methods. The (E)-2-iodo-1-sulfonylalkenes were prepared by the addition of sulfonyl iodides to alkynes while the (Z)-2-iodo-1-sulfonylalkenes were prepared by the copper catalyzed addition of hydrogen iodide to (alpha), (beta)-acetylenic sulfones. The stereochemistry of these (E)- and (Z)-2-iodo-1-sulfonylalkenes was unequivocally established by their stereospecific reduction with zinc and acetic acid to known compounds and by nmr chemical shift data. The substitution reactions of the (E)-2-iodo-1-sulfonylalkenes with monocopper(I) reagents were highly stereospecific and resulted in the exclusive formation of the product of retained configuration. Yields were good to excellent with the major by-product resulting from halogen-metal exchange. The monocopper(I) substitution reactions of the (Z)-2-iodo-1-sulfonylalkenes were also briefly studied. Depending on the temperature of the reaction the product of inverted or retained configuration predominated. Using nmr chemcial shift data the stereochemistry of the substitution products was unequivocally established. The coupling reactions of organocopper reagents with (alpha)-halosulfones were investigated as a means of preparing (alpha)-alkylated sulfones. The starting (alpha)-bromo- and (alpha)-chloro sulfones were prepared by literature methods and characterized by nmr, ir, and mass spectroscopy. The (alpha)-bromo sulfones failed to give good yields of the desired substitution products under a variety of reaction conditions and reagents. The major by-product formed in these reactions was reduced starting material resulting from halogen-metal exchange followed by protonation. The reaction of (alpha)-chlorosulfones with alkyl and arylcopper(I) compounds resulted in good yields of substitution products. Secondary and tertiary alkyl copper(I) compounds gave lower yields of substitution products presumably due to increased steric strain associated with attack by these bulkier groups. Yields of reduced starting material increased with the secondary and tertiary alkyl-copper(I) reagents.
Degree
Ph.D.
Subject Area
Organic chemistry
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