ChemInform Abstract: 1,3‐BIS(TRIMETHYLSILYL)‐1‐ALKYNES. I. PREPARATION FROM PROPARGYLSILANES AND APPLICATION TO THE SYNTHESIS OF α‐FUNCTIONAL ALLENYLSILANES

Abstract

Aus den Propargylsilanen (I) erhält man nach Metallierung mit Trimethylchlorsilan die Bis‐silyl‐Verbindungen (III), die auch aus isomeren Propargylsilanen (IV) erhalten werden können.

Brønsted Acid Catalyzed 1,2-Silyl Shift in Propargyl Silanes: Synthesis of Silyl Dienes and Silyl Indenes

“…9 The second pathway involves a nonvertical stabilization type 10−12 1,2-silyl shift in the intermediate β-silyl vinyl carbenium ion (Scheme 1). In propargyl silanes this was first shown by the Miginiac group, who observed such transformation in 1,4-bis(silyl)alkynes 13,14 and as well as in propargyl silane reactions with acetals. 15 Later Danheiser et al, who had previously reported a very similar annulation of allenyl silanes, 16 reported the synthetic utility of a 1,2-silyl group shift in propargyl silanes (eq Ia, Scheme 1).…”

“…Chemical shifts (δ) are reported in ppm and coupling constants (J) in Hz. Residual solvent ( 1 H) or solvent ( 13 C) peaks were used as internal reference (CDCl 3 , δ 7.26 ppm for 1 H NMR; CDCl 3 , δ 77.16 ppm for 13 C{ 1 H} NMR). Multiplicities are indicated as follows: s (singlet), d (doublet), t (triplet), q (quartet), m (multiplet).…”

“…7) and 3 × H 3 C(2′)), 0.66 (q, 3 J = 7.6 Hz, 3H, H a C(1′)),)), 0.65 (q, 3 J = 7.9 Hz, 3H, H b C(1′)). 13 An oven-dried 500 mL two-necked round-bottom flask equipped with a Teflon-coated magnetic stirrer was evacuated and backfilled with nitrogen three times. Then, hept-1-yn-1-…”

“…1 7)), 0.12 (s, 3H, H 3 C−Si), 0.05 (s, 3H, H 3 C−Si). 13 tert-Butyldimethyl(1-phenylhept-1-yn-3-yl)silane (4ea).…”

“…1 5) and H 2 C(6)), 1.03 (s, 9H, 3 × H 3 C−C−Si), 0.96 (t, 3 J = 6.9 Hz, 3H, H 3 C( 7)), 0.15 (s, 3H, H 3 C−Si), 0.08 (s, 3H, H 3 C−Si). 13 The reaction was performed following general procedure A with 1a (355 mg, 1.69 mmol, 1 equiv), PdCl 2 (15 mg, 0.08 mmol, 0.05 equiv), CuI (48 mg, 0.25 mmol, 0.15 equiv), PPh 3 (89 mg, 0.34 mmol, 0.2 equiv), piperidine (430 mg, 0.50 mL, 5.07 mmol, 3 equiv), and methyl p-bromobenzoate (545 mg, 2.54 mmol, 1.5 equiv). The crude product was purified by flash chromatography on silica gel (hexanes/DCM, 0 → 30% DCM) and then on C18 silica gel (methanol/0.15 M ammonium formate, 80 → 100% MeOH) to give the product 4ga (401 mg, 69% yield) as a pale yellow oil.…”