Reaktionen der Trialkylsilyl‐trifluormethansulfonate, I. Synthese von Trialkylsilyl‐Enolethern

Abstract

Die Ketone 2, 2-Bromketone 6 , a,P-ungesattigte Ketone 8, 1,2-Diketone 10 und aliphatische Aldehyde 20 setzen sich rnit Trialkylsilyl-triflaten 1 in Gegenwart von Triethylamin (4) bei Raumtemperatur zu den Silylenolethern 3,7,9,11 und 21 um. Die Silylierung unsymmetrischer Ketone 12 mit la/4 verlihift rnit uberschussigem l a und 12 regioselektiv im thermodynamischen Sinn zu den Enolethern 13'. Der Reaktionsablauf wird kurz diskutiert. Reactions of Trialkylsilyl Trifluoromethanesulfonates, I. -Synthesis of Trialkylsilyl Enol EthersThe reactions of the ketones 2,2-bromoketones 6 , a$-unsaturated ketones 8, 1,2-diketones, and aliphatic aldehydes 20 with trialkylsilyl triflates 1 in the presence of triethylamine (4) at room temperature yield the silyl enol ethers 3,7,9,11, and 21. The silylation of the unsymmetrical ketones 12 with 1 a/4 runs regioselectively in the thermodynamical sense using 1 a/12 in excess and yields the enol ethers 13'. The course of this reaction is discussed briefly.

Dichloro[TADDOLato(2−)‐ O , O ′]titanium/Dichlorobis[1‐methylethoxy]titanium‐Mediated, Highly Diastereo‐ and Enantioselective Additions of Silyl Enol Ethers to Nitro Olefins and [3+2] Cycloadditions of Primary Adducts to Acetylenes

“…TiCl 4 , 1-(trimethylsilyloxy)cyclohexene, 1-(trimethylsilyloxy)cyclopentene, BSA, phenylacetylene, ethyl 2-butynoate were used as purchased from Fluka. 1-Phenyl-1-(trimethylsilyloxy)ethylene [24], 2-(trimethylsilyloxy)cyclohexa-1,3-diene [25], 1-[(tert-butyl)dimethylsilyloxy]cyclohexene [26], Ti(NMe 2 ) 4 [27], (E)-2-aryl-1-nitro-and 2-heteroaryl-1-nitroethenes [12], and (E)-4-methyl-1-nitropent-1-ene [28] were prepared according to literature procedures. All long-term reactions at below À 788 were carried out using a Lauda Ultra Kryomat 19 ).…”

From a Stable Silanone Complex to Isolable, Donor‐Supported Silicoxonium Halides [LSi(dmap)OSiMe3]+X−

“…When equimolar amounts of Me 3 SiCl were added to a suspension of 1 in toluene at room temperature, the reaction mixture turned to a clear solution immediately, thus indicating the complete conversion of 1. The proton NMR spectrum of the resulting mixture shows the corresponding resonance signals for the free dmap molecule and the Si=O addition product 2 (Scheme 3).…”

“…[12] Although the Si=O double bond in 1 is highly polar and an Si À O single bond is favored in its resonance structures, interestingly, 1 reacts with NH 3 [12] and H 2 S [13] across the Si=O bond to give unique silanoic acid derivatives. In addition, the Si=O moiety in 1 also shows coordination ability by reacting with Lewis acids such as AlMe 3 , thus leading to the stable Lewis acid-base adduct A with a [Si=O!AlMe 3 ] moiety (Scheme 2). [14] The latter reactions prompted us to investigate the reactivity of 1 toward trimethylsilyl halides Me 3 SiX (X = Cl, Br, and I).…”

“…[1] To date, long-lived protonated as well as alkylated carboxonium ions are readily prepared by protonation of the carbonyl compounds with strong acids or by alkylation of the carbonyl compounds using alkyl triflates and so on. [2,3] Even the silylated carboxonium ions, [4] also named siloxycarbenium ions, [5] have been prepared by generation of the trialkylsilyl cation in situ by using the Corey hydride transfer [6] in the presence of ketones, although none of the structures have been proven crystallographically as yet.…”

Iminium Salts by Meerwein Alkylation of Ehrlich’s Aldehyde

“…Exhibiting the interesting motif of a quinoid spacer between an imine moiety and an enol ether, the new bright green iminium salts 1 and 4 ( Figure 1b) belong to the subfamily of quinone imine dyes, featuring specific reactivity patterns on their own [5]. Analogous products of O-alkylation and silylation were obtained from the related 4,4'-bis(dimethylamino)benzophenone [6,7]. Another example was found in 3,6-bis(dimethylamino)-9-ethoxyacridine [8].…”