Synthesis of propargyl alcohols
Asymmetric alkynylation of aldehydes using catalytic amounts of In(III)/BINOL enables a broad range of substrate generality with high enantioselectivity due to the "bifunctional character" of the catalyst activating both substrates.
R. Takita, K. Yakura, T. Ohshima, M. Shibasaki, J. Am. Chem. Soc., 2005, 127, 13760-13761.
The use of N-methylephedrine as chiral additive enables a practical synthesis of propargylic alcohols from terminal alkynes and aldehydes as readily available starting materials. N-Methylephedrine can be purchased in either enantiomeric form as an inexpensive commodity chemical.
D. E. Frantz, R. Fässler, E. M. Carreira, J. Am. Chem. Soc., 2000, 122, 1806-1807.
Enantioselective additions of terminal acetylenes to aldehydes mediated by Zn(OTf)2 and (+)-N-methyl ephedrine can be conducted in reagent grade toluene containing up to 1000 ppm H2O. Products are isolated in high yield and high enantioselectivities.
D. Boyall, D. Frantz, E. M. Carreira, Org. Lett., 2002, 4, 2605-2606.
In an asymmetric addition of lithium acetylides to carbonyl compounds in the presence of a chiral lithium binaphtholate catalyst, slow addition of the carbonyl compound improved the enantioselectivity. This reaction afforded diverse chiral secondary and tertiary propargylic alcohols in high yields and with good to high enantioselectivities.
S. Kotani, K. Kukita, K. Tanaka, T. Ichibakase, M. Nakajima, J. Org. Chem., 2014, 79, 4817-4825.
Schiff-base amino alcohols derived from L-phenylglycine are highly effective ligands for the enantioselective addition of phenylacetylene to aromatic ketones to give optically active tertiary propargylic alcohols.
C. Chen, L. Hong, Z.-Q. Xu, L. Liu, R. Wang, Org. Lett., 2006, 8, 2277-2280.
A broad range of terminal alkynes add rapidly and efficiently to aldehydes via a catalytically generated zinc acetylide in the presence of TMSOTf. In the absence of TMSOTf, no reaction is observed.
C. W. Downey, B. D. Mahoney, V. R. Lipari, J. Org. Chem., 2009, 74, 2904-2906.
Tetrabutylammonium fluoride (TBAF) is a very efficient catalyst for a mild and operationally simple addition of trialkylsilylalkynes to aldehydes, ketones, and trifluoromethyl ketones in THF at room temperature. The reaction conditions tolerate various aryl functional groups, such as chloro, trifluoromethyl, bromo, and fluoro groups. Product yields are generally better than or comparable to those in the literature.
V. R. Chintareddy, H. Wadhwa, J. G. Verkade, J. Org. Chem., 2011, 76, 4482-4488.
Commercially available 2 M Me2Zn in toluene is able to promote the addition of phenylacetylene to aldehydes and ketones. This reactivity is determined by a new mechanism, which is discussed. Broad scope, high tolerance to functional groups, and a simple procedure make this new method highly interesting.
P. G. Cozzi, J. Rudolph, C. Bolm, P.-O. Norrby, C. Tomasini, J. Org. Chem., 2005, 70, 5733-5736.
A novel InBr3-Et3N reagent system promotes the alkynylation of not only a variety of aromatic/heterocyclic or bulky aliphatic aldehydes but also N,O- or N,S-acetals. The reaction of N-silyl-N,O-acetals with 1-alkynes gives primary propargylic amines in good yields.
N. Sakai, R. Kanada, M. Hirasawa, T. Konakahara, Tetrahedron, 2005, 61, 9298-9304.
Inexpensive BINOL in combination with Ti(OiPr)4 catalyzes the reaction of alkynylzinc reagents with a broad range of aldehydes to generate chiral propargyl alcohols with high enantioselectivity at room temperature.
L. Liang, T. T.-L. Au-Yeung, A. S. C. Chan, Org. Lett., 2002, 4, 3799-3801.
A new method for the coupling of aldehydes or ketones with alkynyl propiolates in the absence of a base was developed. The reagents involved in this coupling reaction are easy to handle and tolerate various functional groups.
S. P. Shani, K. Koide, Angew. Chem. Int. Ed., 2004, 43, 2525-2527.
A carbenoid Fritsch-Buttenberg-Wiechell (FBW) rearrangement of a substituted dibromoolefinic precursor is used to generate a lithium acetylide, and subsequent trapping with carbon-based electrophiles provides a wide range of di- and triynes. The lithium acetylide formed from the FBW reaction can also undergo transmetalation to provide zinc, copper, tin, or platinum acetylides.
T. Luu, Y. Morisaki, N. Cunningham, R. R. Tykwinski, J. Org. Chem., 2007, 72, 9622-9629.