(1; R = -CH(CH2)4O)

[14420-47-4]  · C8H11BrO2  · 1-Bromo-3-tetrahydropyranyloxy-1-propyne  · (MW 219.08) (2; R = SiMe3)

[56958-33-9]  · C6H11BrOSi  · 1-Bromo-3-trimethylsilyloxy-1-propyne  · (MW 207.14)

(alkoxymethylalkynylating agent; propargyl alcohol cation equivalent)

Physical Data: (1) bp 69 °C/0.8 mmHg; (2) bp 34-36 °C/2 mmHg.

Solubility: sol any common organic solvent.

Preparative Methods: by protection of 3-bromo-2-propynol: (1) with 3,4-Dihydro-2H-pyran and a catalytic amount of 10 N HCl,1 scale 0.5 mol, yield 60%; (2) by treatment with Sodium Hydride and Chlorotrimethylsilane,2 scale 0.5 mol, yield 70%. 3-Bromo-2-propynol is prepared from Propargyl Alcohol and Bromine in basic medium,3 scale 0.5 mol, in quantitative yield. Conversely, 1-tetrahydropyranyloxy-2-propyne can be brominated with N-Bromosuccinimide and Silver(I) Nitrate in acetone4 (scale 3 mmol, yield 59%).

Handling, Storage, and Precautions: use in a fume hood; store in the absence of moisture, preferably over K2CO3, at 0 °C in the dark.

Electrophilic Propargylation with (1).

A limited number of nucleophiles have been reacted with this reagent to date; an example is sodium diethyl phosphite, which leads to phosphonates (eq 1).

Vinylcopper reagents lead to enynols (eq 2) provided that 1.2-2 equiv of TMEDA are added4 to prevent the formation of diene and diyne.

Vinyl zincacyanocuprates derived from tin also react (eqs 3 and 4).5 The starting copper reagents are made in situ via stannyl cupration. A Cadiot-Chodkiewicz coupling, with a terminal alkyne, leads to the corresponding diynol.6

Electrophilic Propargylation with (2).

Vinylcopper reagents react similarly (eq 5) and are used to prepare (Z,E)-dienols of high purity (after LAH reduction). The reaction described in eq 2 with this reagent affords the same alcohol (82% yield). Also, the use of (2) in eq 4 leads to the corresponding silylated enynol in 65% yield.

Higher Homolog.

The compound Br-C&tbond;C-(CH2)2OSiMe3 is prepared analogously from the bromo alcohol.4 Vinyl cuprates derived from acetylene react better if they are first converted to the vinylcopper species with CuI (eq 6).7

1. Sturtz, G.; Charrier, C.; Normant, H. BSF(2) 1966, 1707.
2. (a) Normant, J. F.; Commerçon, A.; Villieras, J. TL 1975, 1465. (b) Commerçon, A.; Normant, J. F.; Villieras, J. T 1980, 36, 1215.
3. (a) Strauss, F.; Kollek, L.; Heyn, W. CB 1930, 63, 1868. (b) Miller, S. I. OSC 1973, 5, 921.
4. Hofmeister, H.; Annen, K.; Laurent, H.; Wiechert, R. AG(E) 1984, 23, 727.
5. Magriotis, P. A.; Scott, M. E.; Dim, K. D. TL 1991, 32, 6085.
6. Kamenski, A. B.; Smushkevich, Yu. I.; Livshits, A. I.; Suvorov, N. N. ZOR 1980, 16, 758 (CA 1980, 93, 71 460f).
7. Alexakis, A.; Cahiez, G.; Normant, J. F. S 1979, 826.

Jean F. Normant

Université Pierre et Marie Curie, Paris, France

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