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Synthesis of Structures of (Acyloxy)boranes Synthesis of Structures of (Acyloxy)boranes
Author(s) -
Lang Andreas,
Nöth Heinrich,
Schmidt Martin
Publication year - 1995
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19951280803
Subject(s) - chemistry , oxalate , oxalic acid , bicyclic molecule , boranes , stereochemistry , lewis acids and bases , nuclear magnetic resonance spectroscopy , crystal structure , medicinal chemistry , organic chemistry , catalysis , boron
9‐Borabicyclo[3.3.1]nonane (9‐BBNH) reacts with monocarboxylic acids to afford 9‐(acyloxy)‐9‐borabicyclo[3.3.1]nonanes which are dimers in the solid state as shown by X‐ray crystal structures of the benzoate and pivalate. More complex reactions were observed by allowing 9‐BBNH to react with dicarboxylic acids in THF or monoglyme. Thus, (9‐BBN) 2 oxalate 3 contains a fully delocalized oxalate unit with equal C‐O and B‐O bond lengths. Traces of water convert it into the tetrakis(9‐BBN) oxalate 5 . A rather unusual structure is veryfied by 9‐BBN 2,2‐dimethylmalonate 7 which according to its molecular structure is a tetramer featuring a 32‐membered ring system. In contrast, reactions of oxalic acid with thexylborane leads to reduction of the acid and formation of a bicyclic dioxaborolo‐dioxaborolane 10 . Several intermediates were detected by 11 B‐NMR spectroscopy as well as in reactions of BH 3 · THF or BH 3 · SMe 2 with oxalic acid. — It follows from the present study that (acyloxy)boranes derived from dicarboxylic acids are strong Lewis acids with an unexpected variety of structural features.