NH<sub>4</sub>HF<sub>2</sub> as a Selective TBS-Removal
Reagent for the Synthesis of Highly Functionalized Spiroketal via
Tandem Deprotection/Spiroketalization Procedure
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Abstract
NH<sub>4</sub>HF<sub>2</sub> has been used for the first time to
selectively remove the TBS protecting groups from diol ketone precursors
in the synthesis of highly functionalized spiroketals. This method
allows the synthesis of [5,6], [6,6], and [6,7] spiroketal skeletons,
as well as benzannulated spiroketal with retention of acid-sensitive
groups. In this way, spiroketals can be synthesized with diverse substituent
groups in the skeleton or on side chains. To demonstrate the utility
of this methodology, the diverse transformations of highly functionalized
spiroketal <b>3f</b> were also investigated