Sequential alkynylation of ω-bromoalkyl triflates: facile access to unsymmetrical non-conjugated diynes including precursors to diene pheromones

Facile and Efficient Syntheses of (3Z,6Z,9Z)-3,6,9-Nonadecatriene and Homologues: Pheromone and Attractant Components of Lepidoptera

“…R-Linolenic acid [(9Z,12Z,15Z)-9,12,15-octadecatrienoic acid] was selected as starting material because it was commercially available and contained the required unsaturation and geometric configurations. The R-linolenic acid was cleanly converted into the corresponding alcohol, (9Z,12Z,15Z)-9,12,15-octadecatrien-1-ol 2, in 97% isolated yield by reduction with lithium aluminum hydride (LAH) in ether under inert atmosphere (18). An improvement that could be made is to convert the R-linolenic acid to the methyl ester first and then reduce it with LAH to the alcohol.…”

“…It seemed that the (9Z,12Z,15Z)-9,12,15-octadecatrienyl triflate might be a good candidate for sequential coupling reaction with Grignard reagents. Treatment of the (9Z,-12Z,15Z)-9,12,15-octadecatrienyl triflate 3, which was easily prepared from (9Z,12Z,15Z)-9,12,15-octadecatrien-1-ol 2, trifluromethanesulfonic anhydride, and pyridine in dichloromethane (22,23), with methyl magnesium bromide in the 11) also involves multiple steps and produces low yields although the geometric configuration was retained. Furthermore, the routes via coupling reaction of (2Z,5Z,8Z)-2,5,8-undecatrienyl bromide (14) or of (9Z,12Z,15Z)-9,12,15-octadecatrienyl tosylate (25) with appropriate Grignard reagents only give 35% and 48% yields of target compounds, respectively, which were hardly satisfactory.…”

“…It seemed that the (9 Z ,12 Z ,15 Z )-9,12,15-octadecatrienyl triflate might be a good candidate for sequential coupling reaction with Grignard reagents. Treatment of the (9 Z ,12 Z ,15 Z )-9,12,15-octadecatrienyl triflate 3 , which was easily prepared from (9 Z ,12 Z ,15 Z )-9,12,15-octadecatrien-1-ol 2 , trifluromethanesulfonic anhydride, and pyridine in dichloromethane ( , ), with methyl magnesium bromide in the presence of a catalytic amount of Li 2 CuCl 4 at −78 °C for 20 min, and then at −10 °C for 1 h in diethyl ether led to the clean formation of the expected (3 Z ,6 Z ,9 Z )-3,6,9-nonadecatriene 1a in 94% isolated yield from alcohol 2 ( Scheme 1 ). The homologues (3 Z ,6 Z ,9 Z )-3,6,9-eicosatriene 1b , (3 Z ,6 Z ,9 Z )-3,6,9-heneicosatriene 1c , (3 Z ,6 Z ,9 Z )-3,6,9-docosatriene 1d , and (3 Z ,6 Z ,9 Z )-3,6,9-tricosatriene 1e were also obtained from the (9 Z ,12 Z ,15 Z )-9,12,15-octadecatrien-1-ol 2 in the same manner with the appropriate alkyl Grignard reagents in 92, 93, 93, and 94% isolated yields, respectively.…”

Elucidating Structure-Bioactivity Relationships of Methyl-Branched Alkanes in the Contact Sex Pheromone of the Parasitic Wasp Lariophagus distinguendus

“…A solution of 1-heneicosyne (1.23 g, 4.2 mmol) [ 45 ] in 10 mL of dry THF was cooled to −10 °C, n -BuLi (2.89 M in hexanes, 1.46 mL, 4.22 mmol) was added dropwise over 10 min, and the reaction was stirred for 1 h. Alkyl triflate 13 (1.07 g, 4.3 mmol) in 5 mL THF was then added by syringe pump over 30 min, and the reaction was stirred at −10 °C for 5 h. The reaction was quenched with water (20 mL) and extracted with hexane. The hexane extract was washed with brine, dried and concentrated, and the residue was purified by vacuum flash chromatography (hexane) to afford ( R )-5-methylheptacos-7-yne [( R )- 14 ] (1.35 g, 80%) [ 46 ].…”

Synthesis of Marine Polyacetylenes Callyberynes A−C by Transition-Metal-Catalyzed Cross-Coupling Reactions to sp Centers

“…Initially, we chose a triflate as the alkylating agent since alkynylation of alkyl triflates with alkynyllithiums is known to occur under relatively mild conditions . Therefore, Z -10-trifluoromethanesulfonyloxy-1-triisopropylsilyldec-3-en-1-yne ( 37a ) was prepared from alcohol 36 by treatment with Tf 2 O and pyridine in toluene at 0 °C (Scheme ).…”