Photoinduced Multicomponent Synthesis of α-Silyloxy Acrylamides, an Unexplored Class of Silyl Enol Ethers

Abstract

The photoinduced, multicomponent reaction of α-diazoketones, silanols, and isocyanides affords α-silyloxy acrylamides, formally derived from α-keto amides. The presence of a secondary amido group makes classic preparative methods for silyl enol ethers unfeasible in this case, while the mild conditions required by this photochemical approach allow their synthesis in good yields; moreover, the general structure can be easily modified by varying each component of the multicomponent reaction. Fine-tuning of the reaction conditions (i.e., solvents, radiation, additives) can be exploited to obtain complete Z selectivity. The reactivity of this overlooked class of silyl enol ethers has been investigated, and features that could pave the way to new applications have been found.

Ketene 3‐Component Staudinger Reaction (K‐3CSR) to β‐Lactams: A New Entry in the Class of Photoinduced Multicomponent Reactions

“…This novel Ketene 3‐Component Staudinger Reaction (K‐3CSR) adds on the already reported K‐3CR [4a] and SK‐3CR [4d] and further demonstrates the versatility of photoinduced multicomponent reactions [16] . Combinatorial libraries of β‐lactams can be now prepared in a straightforward manner, without preliminary preparation of the imine derivatives, and further developments will be reported in due course.…”

Stereoselective Synthesis of 3,5‐Dihydroxypyrrolidin‐2‐ones Through a Photoinduced Multicomponent Reaction Followed by Dimerization

“…Diazoketones were employed as source of elusive ketenes, generated in situ through a photoinduced Wolff's rearrangement. Within this context we have recently reported that carboxylic acids can be replaced by silanols, thus affording α‐amido silyl enol ethers 1 in a straightforward manner, according to what we have named Sililative Ketene‐Three‐Component‐Reaction (Sililative K‐3CR) (Scheme ) . The methodology allowed the obtainment of a class of compounds that could hardly been synthetized by other means, further demonstrating how the combination of multicomponent approaches with light‐driven processes can widen the variety of chemical structures achievable …”

“…The typical reactivity of silyl enol ethers, combined with the presence of an amide functionality, prompted us to investigate the reactivity of molecules of general formula 1 , taking also into account that compounds 1 could be considered as synthetic analogues of α‐ketoamides. Almost by chance we discovered that, upon treatment with tetrabutylammonium fluoride, silyl enol ether 1a (Scheme ) afforded a new product in 70 % isolated yield, having a MW of 518. Its 1 H‐NMR ([D 6 ]DMSO) displayed only one amidic proton at 6.99 ppm, together with two singlets at 6.16 and 5.32 ppm, presumably belonging to two OH groups.…”

“…The choice for triethylsilanol, instead of triphenylsilanol was made in order to have a more labile silyl group. The reaction of 6 with silyl enol ether 1g was performed under various conditions. We investigated if the nature of solvent, the temperature, the number of equivalents or the order of addition of the reagents could influence the selectivity of the reaction towards the unsymmetrical pyrrolidin‐2‐one.…”

The 100 facets of the Passerini reaction

“…The scope of the reaction was quite broad, and also in this case triphenyl silanol performed better than others ( Scheme 23 ). 57 …”