A series of self-assembled ligands (SALs) were prepared and used in combination with Rh(I) to form a series of heterobimetallic supramolecular catalysts for the catalytic asymmetric hydroboration (CAHB). Using a combinatorial approach SALs A1 and A2 were found to exhibit moderate-to-good levels of substrate selectivity in the CAHB of an equimolar mixture of meta- and ortho-substituted styrenes; SAL A1 reacts faster with the meta-derivative, while SAL A2 reacts preferentially with the ortho-derivative (see below). The present work is focused on studying the influence of the bisoxazoline subunits that direct the self-assembly of the SAL. New indenyl-derived SALs B1 and B2 are examined in the CAHB. Methods for synthesizing the new indenyl SALs, comparison of SALs A and B indicating a significant role of the bisoxazoline subunit in substrate recognition, and the results obtained with 4,4,5,5-tetramethyl-1,3,2-dioxaborolane (pinBH) and 4,4,6-tri-methyl-1,3,2-dioxaborinane (tmdBH) will be discussed.

New self-assembled ligands for substrate-selective catalytic asymmetric hydroboration

248th National Meeting (2014)

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