Influences of Steric Factors on the Reactivity and Structure of Diorganoalkoxysilylamides

Abstract

The combination of an alkoxy and an amino function combined in one silane is rarely found due to the difficult synthesis and isolation.[1] However, this combination offers unique opportunities to investigate the influence of steric requirements or the size of a metal on the structure or reactivity of alkoxysilylamides towards electrophiles by varying the metallating reagent (n‐butyllithium or di‐n‐butylmagnesium) or the organo group on the amino function. For this purpose, we synthesized two alkoxyaminosilanes with acidic NH units that can be metalated. On the one hand, the tert‐butylamino‐substituted (tert‐butylamino)‐methoxydiphenylsilane (1) and on the other hand the isopropylamino‐substituted methoxydiphenyl(isopropylamino)silane (2). The resulting structures showed an interesting interrelation between the Si–O or Si–N bond lengths and the strength of the coordinative bond to the corresponding metal cation (lithium or magnesium).

Primary Amine Functionalization of Alkoxysilanes: Synthesis, Selectivity, and Mechanistic Insights

“…Ph 2 (MeO)Si(NH-i-Pr) (4). 1 H NMR (400 MHz, C 6 D 6 ): δ 0.98 [d, 6H, 3 J HH = 6.24 Hz; SiNCH(CH 3 ) 2 ], 1.24 (d, 1H, 3 J HH = 10.27 Hz; SiNH), 3.07−3.19 [dspt, 1H, 3 J HH = 6.24 Hz,10.39 Hz;SiNCH(CH 3 ) 2 ], 3.55 (s,3H;SiOCH 3 ),6H;CH meta,para ),4H;CH ortho Me 2 (MeO)Si(NH-i-Pr) (8). 1 H NMR (400 MHz, C 6 D 6 ): δ 0.09 (s, 6H; SiCH 3 CH 3 ), 0.57 (br m, 1H; SiNH) 1.00 [d, 6 H, 3 J HH = 6.33 Hz; SiNCH(CH 3 ) 2 ], 3.05 [dspt, 1H, 3 J HH = 6.33 and 10.27 Hz; SiNCH(CH 3 ) 2 ], 3.36 (s, 3H; SiOCH 3 ).…”

“…The resulting alkoxyaminosilanes C enable further functionalization on the silicon-bound NH unit because of its increased acidity as result of the α effect of silicon . Such types of compounds, and, in particular, their N-metalated derivatives, have already been used in coordination compounds. , However, because the synthesis of these mixed functionalized compounds via chlorosilanes is difficult and inefficient, the examples are scarce and limited to bulky substituents on nitrogen. Given the need for new silylation reagents, efficient protecting groups in synthetic chemistry, and effective building blocks in polymer and materials science, the synthesis reported herein could pave the way for a variety of N,O-functionalized silicon precursors.…”

Crystal structure and Hirshfeld surface analysis of (S)-N-methyl-1-phenylethan-1-aminium chloride

“…Compound 2 and its derivatives are characterized by well-known methods of enantiomeric resolution (Ingersoll, 1937;Baltzly & Russell, 1953). The synthesis of Si-N-functionalized silanes starting from chlorosilanes in combination with amines is also very well known (Sakaba et al, 2015;Zibula et al, 2020). However, the formation of the undesirable ammonium chloride is often observed as a byproduct, which is also soluble in small amounts of selected organic solvents.…”

Unusual Coordination Pattern of the Lithium Center in a Chiral α-Lithiated Silicon Compound

“…The silicon-bound methoxy group is a crucial structure-forming coordinating substituent, and the additional presence of an Si–N bond appears to increase the coordination ability of the Si–OMe moiety significantly. This is an important finding that has recently led to the development of novel chiral ligand systems based on aminomethoxysilanes for the deaggregation of alkyllithium reagents. , The interplay between Si–N and Si–O bonds in aminodisiloxanes and methoxysilylamides has also recently been investigated. The three-coordinate lithium center in ( u - 3 ) 2 has an uncommon distorted-trigonal-planar geometry with an angular sum of 356.7(5)°.…”

“…This is an important finding that has recently led to the development of novel chiral ligand systems based on aminomethoxysilanes for the deaggregation of alkyllithium reagents. 6,12 The interplay between Si−N and Si−O bonds in aminodisiloxanes 13 and methoxysilylamides 14 has also recently been investigated. The three-coordinate lithium center in (u-3) 2 has an uncommon distorted-trigonal-planar geometry with an angular sum of 356.7(5)°.…”