Carbamoyl silanes preparation

V,7V-Diethylcarbamoyl trimethylsilane has been prepared by the reaction of bis(trimethylsilyl) sulphide with bis(A,A-diethylcarbamoyl) mercury (Scheme 30)16. Silylation of the carbamoyl cuprate reagent derived from a lithium amide, by addition of copper(I) cyanide and subsequent exposure to carbon monoxide (1 atm), is also effective75,110. Poor to moderate yields of carbamoyl silanes may be isolated by treatment of lithium silylamides with carbon monoxide and methyl iodide, in a reaction sequence involving a nitrogen to carbon silyl shift in an intramolecular silylation (Scheme 31)111. 

The lithium salts of acyclic secondary amines 92 can be conveniently transformed into the corresponding carbamoyllithiums 89 at —78 °C. Under these reaction conditions they react with trialkyltin chlorides to give carbamoyl stannanes 93 (Scheme 24)98. In the case of benzyl and allyl halides, an alkylation can occur affording products 94. However, when trialkylsilyl chlorides were used as electrophiles no carbamoyl silanes could be detected.. V-Alkyl thiocarbamates 95 can be prepared by reaction of the same intermediates 89 with sulfur followed by. S -alkylation at 0°C (Scheme 24)". 

Carbamoyl silanes 100 could be prepared by reaction of lithium silylamides 97 with CO at room temperature and under pressure (30 atm) followed by reaction with methyl iodide (Scheme 25)101. The intermediate carbamoyllithium 98 suffers a rearrangement of the silyl group to afford a new lithium (silylcarbonyl)amide 99, which is finally methylated. 

Cunico and Maity published another example of palladium-catalyzed CO-free carbonylation of aryl halides [121]. Depending on the substrate, 2 mol% of either Pd(PPh3)4 or Pd(P Bu3)2 was used to catalyze the reaction of heteroaryl and aryl bromides with A,A -dimethyl-carbamoyl(trimethyl)silane (Scheme 2.10). Tertiary amides were prepared in good yields by direct carbamoylation under their conditions. Remarkably, chlorobenzene, 1-chloro -methoxybenzene, and iodoben-zene gave the desired products in 74, 78, and 60 % yields, respectively. 

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See also in sourсe #XX -- [ , ]

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