[81302-80-9] · C7H16OSi · 2-Trimethylsilylmethyl-2-propen-1-ol · (MW 144.32)
(derivatives function as trimethylenemethane (TMM) precursors and undergo cyclopentannulation reactions; methylenecyclopentanes; 2-acetoxymethyl-3-trimethylsilylpropene;2 [3 + 2] annulation;3 three-carbon condensative expansion;4 cyclocontraction-spiroannulation5)
Alternate Names: 2-(hydroxymethyl)-3-trimethylsilylpropene; 2-(hydroxymethyl)-2-propenyltrimethylsilane; (hydroxymethyl)allyl trimethylsilane; 2-(trimethylsilylmethyl)allyl alcohol.
Physical Data: bp 54-56 °C/2 mmHg; n
Solubility: insol water; sol all organic liquids.
Form Supplied in: liquid, 90% pure; remainder of the mixture (approx. 10%) is 3-trimethylsilyl-2-methyl-2-propen-1-ol or 3-trimethylsilylmethyl-2-propen-1-ol.
Preparative Method: prepared in four steps from methallyl alcohol. The synthesis begins with the metalation with n-Butyllithium (2 equiv) producing the dianion which is bis-silylated by trapping with Chlorotrimethylsilane to generate the allylsilane. The TMS ether is subsequently removed by hydrolysis (eq 1). The primary allylic alcohol serves as a precursor to more functionalized reagents.
Useful derivatives of the alcohol are the primary allylic chloride, mesylate, and acetate. These are easily prepared in a short number of steps as shown (eq 2) or by functionalization of the primary allylic alcohol.
Purification: by distillation under reduced pressure.
Handling, Storage, and Precautions: flammable liquid; irritant; store at 0-4 °C.
The title allylsilane reagent has been employed as a conjunctive reagent which is considered to be a synthetic equivalent of a zwitterionic, bifunctional compound possessing a nucleophilic allylic anion synthon and an electrophilic cation synthon in the same molecule (1).
The primary allylic halide 2-Chloromethyl-3-trimethylsilyl-1-propene or the mesylate derived from the corresponding alcohol behaves as a bifunctional reagent possessing both nucleophilic and electrophilic reaction centers. For example, they have been shown to participate in [3 + 2] carbon annulations for the construction of methylenecyclopentanes. The reaction proceeds through a Lewis acid-promoted conjugate addition (Sakurai reaction) followed by an internal alkylation of the derived ketone enolate (eq 3).
In a related study, the annulation is combined with a ring expansion reaction. The reaction utilizes a b-keto sulfone as the two-carbon component along with an allylic mesylate as the bifunctional reagent. The alkylation/cyclization process is outlined in eq 4. The subsequent ring expansion appears to be a general process except for cases involving fused six- and seven-membered ring systems (eq 5).
The acylated derivative 2-acetyloxymethyl-3-trimethylsilylpropene is known to be an effective three-carbon component in cyclopentane annulations. It has been demonstrated that 2-acetoxymethylallyltrimethylsilane adds to a variety of electron-deficient alkenes in the presence of a catalytic amount of Tetrakis(triphenylphosphine)palladium(0) and 1,2-Bis(diphenylphosphino)ethane to produce methylenecyclopentanes (eqs 6-8).
The mesylate derivative of 2-hydroxymethyl-3-trimethylsilylpropene participates in an interesting annulation reaction involving a b-keto sulfone as the two-carbon component (eq 9).
The reaction is thought to involve a pinacol-type rearrangement in which the phenylsulfonyl group serves as a leaving group in the presence of a Lewis acid (eq 10).
James S. Panek & Pier F. Cirillo
Boston University, MA, USA