Gini Andrea, Paraja Miguel, Galmés Bartomeu, Besnard Celine, Poblador-Bahamonde Amalia I, Sakai Naomi, Frontera Antonio, Matile Stefan
Department of Organic Chemistry , University of Geneva , Geneva , Switzerland . Email:
Department de Química , Universitat de les Illes Balears , Palma de Mallorca , Spain.
Chem Sci. 2020 Jun 25;11(27):7086-7091. doi: 10.1039/d0sc02551h. eCollection 2020 Jul 21.
Pnictogen-bond donors are attractive for use in catalysis because of deep σ holes, high multivalency, rich hypervalency, and chiral binding pockets. We here report natural product inspired epoxide-opening polyether cyclizations catalyzed by fluoroarylated Sb(v) > Sb(iii) > Bi > Sn > Ge. The distinctive characteristic found for pnictogen-bonding catalysis is the breaking of the Baldwin rules, that is selective cyclization into the -fused ladder oligomers known from the brevetoxins. Moreover, tris(3,4,5-trifluorophenyl)stibines and their hypervalent stiborane catecholates afford different -Baldwin stereoselectivity. Lewis (SbCl), Brønsted (AcOH) and π acids fail to provide similar access to these forbidden rings. Like hydrogen-bonding catalysis differs from Brønsted acid catalysis, pnictogen-bonding catalysis thus emerges as the supramolecular counterpart of covalent Lewis acid catalysis.
由于存在深σ空穴、高多价性、丰富的超价性和手性结合口袋，氮族元素键供体在催化中具有吸引力。我们在此报告了受天然产物启发的环氧开环聚醚环化反应，该反应由氟代芳基化的Sb(v) > Sb(iii) > Bi > Sn > Ge催化。氮族元素键催化的独特特征是打破了鲍德温规则，即选择性环化形成从短裸甲藻毒素中已知的稠合梯状低聚物。此外，三(3,4,5-三氟苯基)锑及其超价锑硼烷邻苯二酚盐具有不同的鲍德温立体选择性。路易斯酸(SbCl)、布朗斯特酸(AcOH)和π酸无法提供进入这些禁环的类似途径。正如氢键催化不同于布朗斯特酸催化一样，氮族元素键催化因此成为共价路易斯酸催化的超分子对应物。
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