Copper (I) Iodide‐Catalyzed One‐Step Preparation of Functionalized Allenes from Terminal Alkynes: Amine Effect

Abstract

An efficient one-step synthesis of functionalized allenes from readily available functionalized terminal alkynes and aldehydes by applying the effect of a dialkylamine has been developed. The protocol is catalyzed by copper(I) iodide and the dialkylamine is believed to play a very important role in the transformation.

CuI‐Catalyzed Synthesis of Functionalized Terminal Allenes from 1‐Alkynes

“…and di( n ‐butyl)amine (1.4 equiv.) in dioxane at 130 °C afforded 1‐(4‐chlorophenyl)buta‐2,3‐dien‐1‐ol ( 2d ) in 67 % yield 7. To develop a general catalytic version to synthesize terminal allenes, we started the initial study by using 1‐phenyl‐2‐propyn‐1‐ol ( 1a ), paraformaldehyde, diisopropylamine, and CuI (10 %) in dioxane at 110 °C.…”

“…This experiment afforded allenol 2a in 88 % yield according to NMR spectroscopic data (Table 1, Entry 1). To improve the yield, the effect of the amine, which was an important parameter in the CuI‐catalyzed synthesis of 1,3‐disubstituted allenes,7 was investigated. Dicyclohexylamine also performed well to give 2a in 84 % yield according to NMR spectroscopic data (Table 1, Entry 2) 6a.…”

Dehydrative Thiolation of Allenols: Indium vs Gold Catalysis

“…Following removal of solvent on a rotary evaporator, the crude product was purified by column chromatography (eluent hexane/ethyl acetate, 4:1) to yield product 3r as a yellow oil (266 mg 1-(4-Chlorophenyl)-buta-2,3-diene-1-ol (3s). 31 A flask was charged with 1-(4-chlorophenyl)prop-2-yn- 1.15 mmol,1.0 equiv),CuI (112.4 mg,0.59 mmol,0.5 equiv), paraformaldehyde (84.9 mg, 2.83 mmol, 2.5 equiv), and dry dioxane (1.7 mL). Diisopropylamine (0.3 mL, 2.07 mmol, 1.8 equiv) was added, and the mixture was heated to reflux for 2 h under argon.…”

“…Purification by column chromatography (eluent hexane/ethyl acetate, 10:1 to5:1) yielded product 3u as a yellow liquid and a 1: 1,1-Diphenylhepta-2,3-dien-1-ol (3v). 31 A flask was charged with 1,1-diphenylprop-2-yn-1-ol (206.5 mg, 0.99 mmol, 1 equiv), freshly distilled butyraldehyde (0.14 mL, 1.58 mmol, 1.6 equiv), CuI Preparation of 1,3-Dienes 4. General procedure C: Using Au(I) Catalysis.…”

A Synthesis of Substituted α-Allenols via Iron-Catalyzed Cross-Coupling of Propargyl Carboxylates with Grignard Reagents

“…21 The latter procedure commonly involves the semistoichiometric use of metals such as copper 21b or cadmium. 22 However, α-allenols, tetra-substituted with respect to the allene moiety are not accessible via the Crabbé reaction.…”