Aza-Peterson Olefinations: Rapid Synthesis of (E)-Alkenes

Abstract

An aza-Peterson olefination methodology to access 1,3-dienes and stilbene derivatives from the corresponding allyl- or benzyl trimethylsilanes is described. Silanes can be deprotonated using Schlosser’s base and added into N-phenyl imines or ketones to directly give the desired products in high yields.

Application of Solid Me3SiZnI for the Synthesis of Aryl and Alkyl Trimethylsilanes

“…The synthetic utility of silylated products was further explored by coupling (4‐methoxyphenyl)trimethylsilane 3 a with 3‐methylthiophene 8 in the presence of 5 mol% Pd(MeCN) 2 Cl 2 and stoichiometric oxidant CuCl 2 in DCE to produce the corresponding coupled product 9 in 70% isolated yield (Scheme 2a) [22] . Additionally, benzyltrimethylsilane 6 d was treated with ( E)−N ,1‐diphenylmethanimine 10 (Aza‐Peterson olefination) in the presence of n‐ BuLi and KO t Bu in THF to produce (E) ‐1,2‐diphenylethene 11 with an isolated yield of 80% (Scheme 2b) [23] …”

“…[22] Additionally, benzyltrimethylsilane 6 d was treated with (E)À N,1-diphenylmethanimine 10 (Aza-Peterson olefination) in the presence of n-BuLi and KO t Bu in THF to produce (E)-1,2-diphenylethene 11 with an isolated yield of 80% (Scheme 2b). [23] In figure 1, we have proposed a plausible mechanism, [21,24] When Ni(II)dtbpy was exposed to Me 3 SiZnI • TMEDA, Ni(0) species is produced, which may be in equilibrium with a weak Ni(0) À SiMe 3 -ate complex. [19b,24-25] In conclusion, we have demonstrated the efficacy of our solid trimethylsilyl zinc reagent in the synthesis of aryl and alkyl trimethylsilanes.…”

Strategic Applications of the β‐Silicon Effect

“…The α-effect is frequently manifested as the metalation of silanes in this position with strong bases, a key step in the Peterson olefination. [6] This effect is significantly less pronounced than the β-silicon effect, and this is reflected by the multitude of studies which have been carried out on the origin and application of the effect. This intense study has manifested itself in the development of methodologies exploiting the formation of these silyl stabilized cations, and it is the purpose of this review to highlight the advances in the development of these reactions in recent years.…”

“…These two phenomena are termed the α‐effect and β‐effect respectively. The α‐effect is frequently manifested as the metalation of silanes in this position with strong bases, a key step in the Peterson olefination [6] . This effect is significantly less pronounced than the β‐silicon effect, and this is reflected by the multitude of studies which have been carried out on the origin and application of the effect.…”