Graduate Thesis Or Dissertation
 

Ring expansion reactions of alkoxides and their application toward synthesis of large ring hormone models

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/st74ct25f

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  • The potassium salts of a series of 1-vinylcycloalk-3-en-l-ols were found to undergo ring expanding [1, 3]-sigmatropic shifts at 25° when dissolved in hexamethylphosphoramide (HMPA) or 1, 2-dimethoxyethane (DME) with 18-crown-6. The yields and reaction rates were compared with those of the corresponding Siloxy-Cope ring expansions. These anionic cases showed about 10¹⁶ to 10¹⁷ faster reaction rates but lower yields. The possible application of this anionic ring expansion to the synthesis of 8:9,13:14-disecosteroids was explored by testing a series of the potassium salts of 6- alkyl -7, 8, 9, 10-tetrahydro-6 (5H)- benzocyclooctenols under the same conditions as above. Alkyl=vinyl, 1, 3-butadienyl, and 1, 3-cis-pentadienyl underwent 2-carbon ring expansions in better yields than the corresponding siloxy-Cope reactions. Alkyl=cyclopropyl or 2-vinylcyclopropyl gave ring fragmentation instead of ring expansion. An open chain example, 2-methyl-l-phenyl-but-3-en-2-ol (potassium salt) was also found to undergo a [1, 3]-sigmatropic shift as well as fragmentation, Other cases, two 1 -vinylcycloalkanols and two 1-viny1-1, 2-cycloalkanediols (potassium salts) failed to undergo ring expansions under these conditions.
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