Mechanistic Investigation of the Staudinger Ligation
摘要:
The Staudinger ligation of azides and phosphines has found widespread use in the field of chemical biology, but the mechanism of the transformation has not been characterized in detail. In this work, we undertook a mechanistic study of the Staudinger ligation with a focus on factors that affect reaction kinetics and on the identification of intermediates. The Staudinger ligation with alkyl azides was second-order overall and proceeded more rapidly in polar, protic solvents. Hammett analyses demonstrated that electron-donating substituents on the phosphine accelerate the overall reaction. The electronic and steric properties of the ester had no significant impact on the overall rate but did affect product ratios. Finally, the structure of an intermediate that accumulates under anhydrous conditions was identified. These findings establish a platform for optimizing the Staudinger ligation for expanded use in biological applications.
A method for making diazo-compounds, diazonium salts thereof and other protected forms of these compounds. Diaz-compounds are prepared by reaction of a tertiary phosphine reagent carrying a reactive carbonyl group with an azide. The reaction can also generate an acyl triazene which can be converted thermally or by addition of base to form the diazo-compound or the acyl triazene can be isolated. The method is particularly useful for conversion of azides carrying one or more electron withdrawing groups to diazo-compounds. The method can be carried out in aqueous medium under mild conditions and is particularly useful for conversion of azido sugars to diazo-compound and diazonium salts thereof under physiological conditions. Tertiary phosphine reagents, particularly those that are water-soluble, and precursors for preparation of the reagents are provided.
Cationic Palladium η<sup>3</sup>-Allyl Complexes with Hemilabile P,O-Ligands: Synthesis and Reactivity. Insertion of Ethylene into the Pd−Allyl Function
作者:Stefan Mecking、Wilhelm Keim
DOI:10.1021/om960061z
日期:1996.5.28
Cationicpalladium allyl complexes [(η3-C3H5)Pd(κ2P∧O)]+SbF6- (2[SbF6], P∧O ≡ Ph2P(CH2)2C(O)OEt; 3[SbF6], o-Ph2PC6H4C(O)OEt; 4[SbF6], Ph2P(CH2)2P(O)Ph2) have been prepared. In all complexes the oxygen donor can be displaced by other ligands such as carbon monoxide and ethylene. Displacement of an ester donor occurs much more readily than displacement of the phosphine oxide function. Above 0 °C, the
阳离子钯络合物烯丙基[(η 3 -C 3 H ^ 5)的Pd(κ 2 P ∧ Ò)] +的SbF 6 - (2 [的SbF 6 ],P ∧ ö ≡博士2 P(CH 2)2 C(Ò) OEt; 3 [SbF 6 ],o -Ph 2 P C 6 H 4 C(O)OEt; 4 [SbF 6 ],Ph 2 P已经制备了(CH 2)2 P(O)Ph 2。在所有配合物中,供氧体可以被其他配体(例如一氧化碳和乙烯)取代。酯供体的置换比氧化膦功能的置换更容易发生。高于0℃,将得到的乙烯配合物[(η 3 -C 3 H ^ 5)的Pd(C 2 H ^ 4)(κ 1 P ~O)] +反应,得到(1,2,5-η 3) -戊-1-烯-5-基配合物[(H 2 ç CH(CH 2)3的Pd(κ 2 P ∧O)] +。的速率常数如ķ(17℃)=(2.27±0.11)×10 - 4个小号- 1被确定为P,O≡博士2 P(CH
Preparation of diazo and diazonium compounds
申请人:Wisconsin Alumni Research Foundation
公开号:US08350014B2
公开(公告)日:2013-01-08
A method for making diazo-compounds, diazonium salts thereof and other protected forms of these compounds. Diaz-compounds are prepared by reaction of a tertiary phosphine reagent carrying a reactive carbonyl group with an azide. The reaction can also generate an acyl triazene which can be converted thermally or by addition of base to form the diazo-compound or the acyl triazene can be isolated. The method is particularly useful for conversion of azides carrying one or more electron withdrawing groups to diazo-compounds. The method can be carried out in aqueous medium under mild conditions and is particularly useful for conversion of azido sugars to diazo-compound and diazonium salts thereof under physiological conditions. Tertiary phosphine reagents, particularly those that are water-soluble, and precursors for preparation of the reagents are provided.
A method for making diazo-compounds, diazonium salts thereof and other protected forms of these compounds. Diazo-compounds are prepared by reaction of a tertiary phosphine reagent carrying a reactive carbonyl group with an azide. The reaction can also generate an acyl triazene which can be converted thermally or by addition of base to form the diazo-compound or the acyl triazene can be isolated. The method is particularly useful for conversion of azides carrying one or more electron withdrawing groups to diazo-compounds. The method can be carried out in aqueous medium under mild conditions and is particularly useful for conversion of azido sugars to diazo-compounds and diazonium salts thereof under physiological conditions. Tertiary phosphine reagents, particularly those that are water-soluble, and precursors for preparation of the reagents are provided.
A method for making diazo-compounds, diazonium salts thereof and other protected forms of these compounds. Diaz-compounds are prepared by reaction of a tertiary phosphine reagent carrying a reactive carbonyl group with an azide. The reaction can also generate an acyl triazene which can be converted thermally or by addition of base to form the diazo-compound or the acyl triazene can be isolated. The method is particularly useful for conversion of azides carrying one or more electron withdrawing groups to diazo-compounds. The method can be carried out in aqueous medium under mild conditions and is particularly useful for conversion of azido sugars to diazo-compound and diazonium salts thereof under physiological conditions. Tertiary phosphine reagents, particularly those that are water-soluble, and precursors for preparation of the reagents are provided.