One-Step Synthesis of Racemic 6-Methyloctan-3-One, an Alarm Pheromone Component of Ants of the Genus Crematogaster

Abstract

Dzhemilev6-Methyloctan-3-one (1) was identified as a component of the alarm pheromone of ants of the genus Crematogaster [1]. Several syntheses of this compound as the racemate and an enantiomer are known [2][3][4][5][6]. However, many of them involve several steps and most are labor-intensive and require costly starting materials.We developed a convenient and effective synthetic pathway for a racemic analog of 1 that was based on our recently proposed regioselective carbonylation of 1-alkenes using Et 2 Zn and TaCl 5 catalyst [7].The reaction of but-1-ene with Et 2 Zn in the presence of TaCl 5 (Et 2 Zn-but-1-ene-TaCl 5 = 110:100:5; Et 2 Zn concentration 1.0 mmol/mL in hexane, 20°C, 5 h) formed organozinc compound 2. For this, hexane (20 mL) was cooled to -15°C and treated with but-1-ene (2.25 ml, 20 mmol) cooled to -30°C. Then, the solution was cooled to -15-20°C, treated with Et 2 Zn (2.25 mL, 22 mmol) and TaCl 5 (0.4 g, 1 mmol), heated gradually to room temperature, stirred for 5 h, cooled to -5°C, and treated dropwise with propionylchloride (3, 1.74 mL, 20 mmol) in hexane. All these operations were performed under a dry Ar atmosphere. The resulting reaction mixture was stirred for 2 h and treated with aqueous HCl solution (10%). The resulting 1 was extracted by Et 2 O (3 u 50 mL). The extracts were dried over anhydrous MgSO 4 . The solvent was distilled off. The residue was chromatographed (SiO 2 , hexane) to afford 1 (2.69 g, 99% pure) in 95% yield based on 3 (Scheme 1).The structure of 1 was proven using IR, PMR, and 13 C NMR spectral methods and GC-MS in addition to comparison with an authentic sample [6]. REFERENCES 1.R. M. Crewe, M. S. Blum, and C. A. Collingwood, Comp.

Recent advances in the synthesis of insect pheromones: an overview from 2013 to 2022

“…(Col., Cerambycidae): 179 , 154 Sitona discoideus (Col., Curculionidae): 180 and (4 S ,5 S )- 181 , 155 Rhinostomus barbirostris (Col., Curculionidae): (4 S ,5 R )- and (4 S ,5 S )- 181 , 156 Sitophylus oryzae and S. zeamais (Col., Dryophthoridae): 181 , 157 Diabrotica undecimpunctata howardi (Col., Chrysomelidae): 182 , 140,158 Crematogaster spp. (Hym., Formicidae): 183 , 159 Hesperophylax occidentalis (Tri., Limnephilidae): 184 , 154 Rhynchophorus ferrugineus (Col., Dryophthoridae): 185 , 160,161 Tribolium spp. (Col., Tenebrionidae): 186 , 162–164 Diabrotica balteata (Col., Chrysomelidae): 187 , 165 Pallantia macunaima (Hem., Pentatomidae): 188 , 166 Lasioderma serricorne (Col., Anobiidae): 189 , 167 Stylops mueller (Str., Stylopidae): 190 , 168 Dociostaurus maroccanus (Ort., Acrididae): 191 , 169,170 Xenos peckii (Str., Xenidae): 192 , 171,172 Matsucoccus thunbergianae (Hem., Margarodidae): 193 .…”

“…The a,b-unsaturated ketone used as the starting material was obtained in 56% isolated yield by aldol condensation of propanal and 3-pentanone. Formicidae): 183, 159 Hesperophylax occidentalis (Tri., Limnephilidae): 184, 154 Rhynchophorus ferrugineus (Col., Dryophthoridae): 185, 160,161 Tribolium spp. (Col., Tenebrionidae): 186, [162][163][164] Diabrotica balteata (Col., Chrysomelidae): 187, 165 Pallantia macunaima (Hem., Pentatomidae): 188, 166 Lasioderma serricorne (Col., Anobiidae): 189, 167 Stylops mueller (Str., Stylopidae): 190, 168 Dociostaurus maroccanus (Ort., Acrididae): 191, 169,170 Xenos peckii (Str., Xenidae): 192, 171,172 Matsucoccus thunbergianae (Hem., Margarodidae): 193.…”