After the mixture was stirred for 3 h, an aldehyde (0.25 mmol) was added and the stirring continued for 8 h. The reaction was quenched with ice and extracted with methylene chloride. 1H NMR (300 MHz, CDCl3) δ 7.51–7.44 (m, 4H), 7.32–7.29 (m, 3H), 7.21–7.19 (d, J = 7.5 Hz, 1H), 5.64 (br, 1H), 2.36 (s, 3H), 2.21 (br, 1H). Anhydrous N,N-dimethylformamide and methyl sulfoxide were used directly from Sure/Seal bottles as purchased (water, <0.005%). Only until recently have highly enantioselective and catalytic alkynylmetal additions been developed. This video is unavailable.
A carbon-carbon triple bond may be located at any unbranched site within a carbon chain or at the end of a chain, in which case it is called terminal.Because of its linear configuration ( the bond angle of a sp-hybridized carbon is 180º ), a ten-membered carbon ring is the smallest that can accommodate this function without excessive strain.
Reaction gives an aldehyde when you preform it with a terminal alkyne, and a ketone when you perform it with an internal alkyne. Retention time: t minor = 40.7 min. Under nitrogen, n-BuLi in hexanes (1.6 M, 0.32 mmol, 0.2 ml) was added into a solution of an alkyne (0.35 mmol) in tetrahydrofuran (3 ml) in a 15-ml flask. HPLC analyses were conducted on the Waters 600 with the Daicel Chiracel OD column eluted with 10% iPrOH in hexane at 1.0 ml/min, detected at 254 nm by Waters 486, unless otherwise indicated. Alkyne react with water in presence of mercuric sulphate (HgSO 4) and dilute sulfuric acid at 333K. The results are summarized in Table 2. 93% ee determined by HPLC analysis. 72% yield. Alkynes can also be hydrated to form enols that immediately tautomerise Terminal alkynes give aldehydes, internal alkynes … 86% yield. In particular, the method using BINOL/Ti(OiPr)4/Et2Zn is highly enantioselective for the reaction of terminal alkynes with a broad range of substrates, including alkyl, aryl, and α,β-unsaturated aldehydes (24, 25). Increasing the amount of HMPA from 2 to 4 equiv in entry 24 reduced the ee. The conditions of entry 22 were applied to the reaction of several alkynes with various aldehydes. The addition of nonpolar E–H bonds across C≡C is general for silanes, boranes, and related hydrides. It is a two step process where first the terminal alkyne is converted into enol and then tautomerization occurs to give corresponding aldehyde. This catalytic method shows high enantioselectivity for the reaction of alkynes with mostly aliphatic aldehydes. 1-Pentafluorophenyl-3-phenyl-prop-2-yn-1-ol. 1-(4-Fluoro-phenyl)-3-phenyl-prop-2-yn-1-ol.