Bu₄N⁺ Alkoxide-Initiated/Autocatalytic Addition Reactions with Organotrimethylsilanes

Abstract

The use of Me 3 SiO − /Bu 4 N + as a general activator of organotrimethylsilanes for addition reactions has been established. The broad scope of the method offers trimethylsilanes (including acetate, allyl, propargyl, benzyl, dithiane, heteroaryl, and aryl derivatives) as bench-stable organometallics that can be readily utilized as carbanion equivalents for synthesis. Reactions are achieved at rt without the requirement of specialized precautions that are commonplace for other organometallics.

Mechanism of Enolate Transfer between Si and Cu

“…Characteristic peaks: Benzaldehyde: 1 H NMR (400 MHz, CDCl 3 ): δ =9.92 ppm (s, 1 H); product A: 1 H NMR (400 MHz, CDCl 3 ): δ =5.02 ppm (dd, J= 8.8, 4.2 Hz, 1 H). These data are in accordance with those previously described …”

“…Product C: 1 H NMR (400 MHz, CDCl 3 ): δ =5.81 (dt, J= 15.7, 1.6 Hz, 1 H), 4.72 ppm (dd, J= 7.7, 5.2 Hz, 1 H). These data are in accordance with those previously described …”

“…These data are in accordance with those previously described. [44] Reaction between dienolate and benzaldehyde:C uCl (74 mg, 0.74 mmol, 1.0 equiv) and MeONa (40 mg, 0.74 mmol, 1.0 equiv) were added to af lame-dried round-bottom flask, dissolved in freshly distilled THF (60 mL), and the solution was stirred at 50 8C for 2h.T he light brown suspension obtained was cooled at room temperature and cannulated into as eparate flame-dried round bottom-flask containing BINAP (463 mg, 0.74 mmol, 1.0 equiv), and freshly distilled THF (2 5mL) was used to rinse the flask. After stirring for 1h at room temperature, freshly distilled benzaldehyde (76 mL, 0.74 mmol, 1.0 equiv) was added, followed by freshly distilled dienolate (160 mL, 0.74 mmol, 1.0 equiv).…”

Highly Selective Addition of a Broad Spectrum of Trimethylsilane Pro‐nucleophiles to N‐tert‐Butanesulfinyl Imines

“…We recently reported that the Lewis base Me 3 SiO À as its Bu 4 N + salt, in THF,c an promote the carbanion reactivity of organo-TMS reagents for addition to carbonyls. [5] In ap reliminary study,i tw as found that the addition of aromatic andh eterocyclic silanes to chiral N-tert-butanesulfinyl imines could be achievedw ith excellent diastereoselectivity. [6] In this account, thesea dditionsh ave been expanded to encompass ab road spectrum of TMS reagents, covering aw ides pan of reactivity,u sing as ingles et of reaction conditions.…”

Direct Synthesis of α‐Allenols from TMS‐Protected Alkynes and Aldehydes Mediated by Tetrabutylammonium Fluoride

“…Based on these data, and noting previous mechanistic reports by Scheidt and Verkade on similar systems, we propose that TBAF removes the TMS protecting group from 1 a to produce an ynide (via a pentavalent silicon intermediate 9 ), which in turn reacts with its respective aldehyde (e.g., 11 ) to produce propargyl silyl enol ether 13 . In the presence of TBAF or TBAH, compound 13 rearranges to α‐allenol 16 as depicted on Scheme . Nevertheless, further studies will be necessary to adequately evaluate this hypothesis.…”