Easy one-step general synthesis of acylsilanes

Direct synthesis and applications of solid silylzinc reagents

The increased synthetic utility of organosilanes has motivated researchers to develop milder and more practical synthetic methods. Silylzinc reagents, which are typically the most functional group tolerant, are notoriously difficult to synthesize because they are obtained by a pyrophoric reaction of silyllithium, particularly Me3SiLi which is itself prepared by the reaction of MeLi and disilane. Furthermore, the dissolved LiCl in silylzinc may have a detrimental effect. A synthetic method that can avoid silyllithium and involves a direct synthesis of silylzinc reagents from silyl halides is arguably the simplest and most economical strategy. We describe, for the first time, the direct synthesis of PhMe2SiZnI and Me3SiZnI reagents by employing a coordinating TMEDA ligand, as well as single crystal XRD structures. Importantly, they can be obtained as solids and stored for longer periods at 4 °C. We also demonstrate their significance in cross-coupling of various free alkyl/aryl/alkenyl carboxylic acids with broader functional group tolerance and API derivatives. The general applicability and efficiency of solid Me3SiZnI are shown in a wide variety of reactions including alkylation, arylation, allylation, 1,4-addition, acylation and more.

Cu-Catalyzed Carbonylative Silylation of Alkyl Halides: Efficient Access to Acylsilanes

A Cu-catalyzed carbonylative silylation of unactivated alkyl halides has been developed, enabling efficient synthesis of alkyl-substituted acylsilanes in high yield. A variety of functional groups are tolerated under the mild reaction conditions, and primary, secondary, and tertiary alkyl halides are all applicable. The practical utility of this method has been demonstrated in the synthesis of acylsilanes bearing different silyl groups as well as in situ reduction of a product to the corresponding α-hydroxylsilane in one pot. Mechanistic experiments indicate that a silylcopper intermediate activates alkyl halides by single electron transfer to form alkyl radical intermediates and that carbon-halogen bond cleavage is not involved in the rate-determining step.

Efficient Synthesis of Acylsilanes Using Morpholine Amides

[reaction: see text] A general synthesis of acylsilanes from the corresponding morpholine amides and silyllithium species is described. The use of morpholine amides is economical and prevents over-addition by the silyl nucleophile. The procedure cleanly affords acylsilanes in good yields and circumvents the use of stoichiometric copper(I) cyanide typically employed to synthesize these compounds from acid chlorides.