Phenylacetylene

Dedicated to Professor Dr. Grzegorz Mlostoń, Dr. Emilia Obijalska, and my family.

Introduction

Phenylacetylene (1-phenylethyne, 1-phenylacetylene) is a terminal alkyne which under standard conditions is a light yellow liquid with a characteristic odor. It can be conveniently prepared via the reaction of benzaldehyde with the Bestmann–Ohira reagent in the presence of a base at room temperature.[1a] Other methods applied for its preparation consists in the treatment of acetophenone with lithium diisopropylamide (LDA) and diethyl chlorophosphate.[1b] Phenylacetylene is widely applied as a versatile building block, for example in Kinugasa reactions, Diels–Alder reactions, 1,3-dipolar cycloaddition reactions, diverse transition-metal-supported coupling reactions, and in nucleophilic additions.

Scheme 1

Abstracts

(A) Phenylacetylene is widely explored as a model acetylenic substrate in Kinugasa reactions. Saito et al. described an enantioselective version of this reaction which was performed in the presence of chiral oxazoline ligands.[2] The reported diastereo- and enantioselectivities were satisfactory, but chemical yields were rather low. In another paper, the applications of modified bis(oxazoline) ligands were reported, and in this case the desired β-lactams were obtained in high chemical yields. In addition, better diastereo- and enantio­selectivities were observed.[3]
(B) Cyclic, achiral, and enantiopure nitrones were used in reactions with phenylacetylene under Kinugasa reaction conditions. In both cases only one diastereoisomer of the desired β-lactam was isolated in low to moderate yield.[4]
(C) Analogous reactions with diverse nitrones in the presence of catalytic amounts of indium tribromide (InBr3) and a tertiary amine led to N-hydroxypropargyl amines in moderate to good yields.[5]
(D) In a three-component reaction, performed in the presence of a catalytic amount of Ni(II)-Y zeolite, phenylacetylene reacted with aldehydes and secondary amines yielding β-ynamines in high to excellent yields.[6]
(E) 1,3-Dipolar cycloadditions of aryl- and alkylazides with phenylacetylene, carried out in the presence of copper(II) salts, sodium iodide, and a base, led to 5-iodo-1,2,3-triazoles formed as the main or exclusive products. However, the formation of 4-unsubstituted 1,2,3-triazoles as side-products was observed in reactions carried out in the presence of copper(II) chlorate(VII).[7]
(F) Heterocyclization of gem-dibromovinylphenols followed by Sonogashira reaction of the initially formed 2-bromobenzofurane with phenylacetylene gave 2-phenylethynyl-substituted benzofurans in high yield.[8] Upon optimizing the reaction conditions, copper(I) iodide, DABCO, and cesium carbonate were used in a one-pot procedure.
(G) In a microwave assisted, palladium-catalyzed tandem reaction, phenylacetylene and 2-bromobenzamide were used for the efficient preparation of isoindolinone derivatives.[9]
(H) The nucleophilic addition of phenylacetylene to isatin derivatives was achieved under copper-mediated C–H bond activation conditions.[10]
(I) 2-Substituted, optically active tetrahydroquinolines were obtained in high chemical yields and with high enantiomeric excess via the reaction of 2-aminobenzaldehydes with phenylacetylene under asymmetric cooperative triple catalysis.[11]

• References

• 1a Möller S, Liepold B, Bestmann HJ. Synlett 1996; 521
• 1b Negishi E, King AO, Klima WL. J. Org. Chem. 1980; 40: 2526
• 2 Saito T, Kikuchi T, Tanabe H, Yahiro J, Otani T. Tetrahedron Lett. 2009; 50: 4969
• 3 Chen J.-H, Liao S.-H, Sun X.-L, Shen Q, Tang Y. Tetrahedron 2012; 68: 5042
• 4 Grzeszczyk B, Poławska K, Shaker S, Stecko Y, Mames MA, Woźnicka M, Chmielewski M, Furman B. Tetrahedron 2012; 68: 10633
• 5 Ji D.-M, Xu M.-H. Tetrahedron Lett. 2009; 50: 2952
• 6 Namitharan K, Pitchumani K. Eur. J. Org. Chem. 2010; 411
• 7 Brotherton WS, Clark RJ, Zhu L. J. Org. Chem. 2012; 77: 6443
• 8 Liu J, Zhang N, Yue Y, Wang D, Zhang Y, Zhang X, Zhuo K. RSC Adv. 2013; 3: 3865
• 9 Hellal M, Cuny GD. Tetrahedron Lett. 2011; 52: 5508
• 10 Chouhan M, Senwar KR, Kumar K, Sharma R, Nair VA. Synthesis 2014; 46: 195
• 11 Patil NT, Raut VS, Tella RB. Chem. Commun. 2013; 49: 570