A New Method for the Preparation of 1,5-Diynes. Synthesis of (4E,6Z,10Z)-4,6,10-Hexadecatrien-1-ol, the Pheromone Component of the Cocoa Pod Borer MothConopomorphacramerella

Abstract

[reaction: see text] A new method for the synthesis of 1,5-diynes, from the reaction of 1,3-dilithiopropyne and propargyl chlorides, was developed. This new methodology was used to prepare (4E,6Z,10Z)-4,6,10-hexadecatrien-1-ol, one of the pheromone components of the cocoa pod borer moth Conopomorpha cramerella, in 51% overall yield.

Synthesis of (4E,6Z,10Z)-hexadeca-4,6,10-trien-1-ol and (4E,6E,10Z)-hexadeca-4,6,10-trien-1-ol, the pheromone components of cocoa pod borer moth Conopomorpha cramerella

“…Potassium bis(trimethylsiyl)amide (300 mL, 0.3 mol, 1 M in THF) was added dropwise over 30 min to a suspension of nhexylphosphonium bromide (128 g, 0.3 mol) in dry THF (600 mL) at 0 C under nitrogen. The resulting orange solution was further stirred for 1 h at 0 C and then cooled to À78 C. A solution of aldehyde 9b (17.6 g, 0.2 mol) in dry THF (200 mL) was added dropwise to the above mixture over 1 h, maintaining the temperature below À70 C. The resulting yellow solution was allowed to slowly warm up to room temperature over a period of 10 h. Then the reaction mixture was quenched with a saturated solution of NH 4 Cl. Aer the complete evaporation of THF, the reaction mixture was extracted with EtOAc (300 mL Â 3).…”

“…Aer a solution of n-BuLi (44 mL, 110 mmol, 2.5 M solution in hexane) was slowly added to the reaction mixture, the mixture was stirred at À70 C for 2 h and then allowed to warm up to room temperature. The reaction mixture was quenched with a saturated solution of NH 4 Cl, and the organic phase was washed with brine, dried over Na 2 SO 4 , and then concentrated. The residue was puried through a silica gel column (eluent: petroleum ether) to afford enyne 13 as a colorless oil (6.83 g, 91% (E)-5-Bromopent-4-en-1-ol (14)…”

“…The extract was washed with water and brine, dried over Na 2 SO 4 , and then concentrated. The residue was puried through a silica-gel column (eluent 4 (1155 mg, 1 mmol) and CuI (209 mg, 1.1 mmol), the reaction mixture was degassed for an additional 10 min. The reaction mixture was stirred overnight and ltered through Celite.…”

“…3 Later, Pereira and Cabezas reported a new method for the synthesis of 1,5-diynes using the reaction of 1,3-dilithiopropyne with propargyl chlorides, and applied this new method to prepare 1a with an overall yield of 51%. 4 Yet, the preparation of 1,5-diynes was complicated, and this compound could not be used as the starting material of isomer 2a. The general utilization of insecticides is limited by their high cost, environmentally unfriendliness and the development of insecticide-resistance.…”

“…The Sonogashira coupling of enol 14 with enyne 13 using Pd(PPh 3 ) 4 as catalyst in dry diethylamine at room temperature gave enynol 15 in 83% yield. 11 The Sonogashira coupling maintained the excellent isomeric purity owing to the moderate conditions used.…”