Recent isolation3 of the sex attractant of the male boll weevil (Anthonomus granáis Boheman) followed a most difficult phase of insect pheromone research4 and allowed structure elucidation4 of the essential components as the monoterpenes 1, 2, and 3 or 4, which have recently been synthesized by nonselective routes.5

Abstract. A very short synthesis of the racemic cecropia hormone has been realized, utilizing a Claisen reaction. Methyl 6-hydroxy-3-methyl-7-methylene-2-trans-nonenoate, on treatment with the dimethyl ketal of 3-chloro-3-methyl-2-pentanone and a catalytic amount of 2,4-dinitrophenol, is transformed directly into methyl 11-chloro-3, 11-dimethyl-7-ethyl-10-oxo-2-trans, 6-trans-tridecadienoate. Selective reduction gives a mixture of diastereoisomeric chlorohydrins separable by chromatography. The predominant threo-chlorohydrin is transformed into the juvenile hormone. R=CH3 We wish to report a very short, stereoselective synthesis6 of the racemic cecropia hormone 1, which for the first time allows easy access to both the natural trans, trans, cis hormone 1 and its all-trans isomer in pure form.Previously, the allylic alcohol 3 has been shown2 to react with the allylic ketal 4, involving a stereospecific Claisen rearrangement, to produce the unsaturated ketone 5. Although this compound contains the complete skeleton of 1, five steps were required to transform ketone 5 into the racemic juvenile

Abstract. Experimental details are reported for a previously described synthesis of cecropia juvenile hormone.Recently we reported a very short stereoselective synthesis of the racemic cecropia juvenile hormone,1 utilizing a novel Claisen reaction. Methyl 6-hydroxy-3-methyl-7-methylene-2-trans-nonenoate, on treatment with the dimethyl ketal of 3-chloro-3-methyl-2-pentanone and a catalytic amount of 2,4-dinitrophenol, is transformed directly into methyl 11-chloro-3,11-dimethyl-7-ethyl-10-oxo-2-trans,6-trans-tridecadienoate. Selective reduction gives a mixture of diastereoisomeric chlorohydrins which is separable by chromatography. The predominant threo-chlorohydrin is transformed into the juvenile hormone. In the present paper we report the experimental details of this synthesis.2 3-Chloro-3-methyl-2-pentanone: To a warm solution (850C) of 123 g (720 mmol) of cupric chloride dihydrate and 22.6 g (540 mmol) of lithium chloride in 200 ml of dimethyl formamide, under nitrogen, was added 30 g (300 mmol) of 3-methyl-2-pentanone. After 4 hr at 85-90'C, ice was added and the product extracted with pentane. The pentane was washed with water until neutral, then with brine, and dried over anhydrous MgSO4. Removal of pentane and distillation through a Vigreux column gave 36 g (90% yield, >99% pure by GLC) of 3-chloro-3-methyl-2-pentanone, bp 88-90°C/148 mm; IR(film) 1718 cm-1; nmr (CDCl3) 6 0.98 (t,