887502-26-3Relevant articles and documents
[1,3]-Transfer of chirality during the nicholas reaction in γ-benzyloxy propargylic alcohols
Diaz, David D.,Ramirez, Miguel A.,Martin, Victor S.
, p. 2593 - 2606 (2008/02/07)
A highly regio- and stereoselective intramolecular [1.5]-hydrogentransfer process is described. Treatment of γ-benzyl-protccted Co 2(CO)6-α,γ-acetylenic diols with BF 3·OEt2 provides bis-homopropargylic alcohols. The reaction occurs within seconds, tolerates a wide range of functionalities, and provides good yields. When the ether group is located at a stereochemically defined carbon atom, the rearrangement occurs with high stereoselectivity, transferring the chirality of the carbinol center to the newly created stereocenter. The cleavage of the benzyloxy group is totally regioselective when additional benzyl ethers are present. The scope and limitations of this novel process in densely substituted substrates are evaluated, and possible competitive reactions and/or stereochemical influences are also described. A mechanism based on a highly ordered chair-like transition state substantiated by a theoretical study is also included.
