Reaction of bulky main group metal(II) amides with polyfunctional phenol substrates

Abstract

Scope and Method of Study: The purpose of this study was to afford the selective protection of one functional group in the presence of others. This is an important process in synthetic chemistry. Several types of silylating agents have been reported for the protection of hydroxyl groups, with limited selectivity, harsh reaction conditions and long reaction times. In an attempt to increase silylation power and limit the complexity and harshness of these reactions we have developed a novel method using mild conditions to achieve silylation of one or two hydroxyl groups. Silyaltion reactions were investigated for the reaction between 3,3'-disubstituted-1,1'-bi-2,2'-napthol and various metal(II) amides. These reactions were monitored using 1H-NMR spectroscopy. Studies were also done involving the reaction of Ge[N(SiMe3)2]2 with calix[4], [6] and [8]arenes. Results were confirmed via 1H-NMR and X-ray Crystallography.

Findings and Conclusions: We have developed a novel method using metal (II) amides under mild conditions to achieve silylation of one or two hydroxyl groups with reaction times ranging from 10min-24hrs. Variation of the metal furnished different rates of reaction. The general trend in reaction rate was monitored by 1H-NMR spectroscopy and decreases in the order M= Be>Zn>Ge>Mg, with no observable silylated products using Sn, Pb or Ca amides. Reactions employing a mercury (II) amide resulted in an unexpected outcome involving cyclization via formation of a C-O bond. The reaction of germanium (II) amide with calix[4], calix[6] and calix[8]arenes resulted in the formation of compounds containing germanium rhombi as well as the formation of a unique compound containing unusual diamidosilyl ether groups.