(E)-1-Benzyl-3-(1-iodoethylidene) (CAS no 146980-71-4), which is also known as Piperidine, 3-(iodoethylidene)-1-(phenylmethyl)-(E)-, could be produced through the following synthetic routes.

A. 4-Hexyn-1-yl methanesulfonate. An oven-dried, 500-mL, one-necked, round-bottomed flask equipped with a magnetic stirring bar is flushed with argon and 260 mL of dichloromethane is added. The flask is sealed with a rubber septum inlet and cooled to ca. -10°C in an ice-salt bath. To this flask are added via syringe 11 mL (80 mmol) of triethylamine, 5.0 g (51 mmol) of 4-hexyn-1-ol, and 4.3 mL (56 mmol) of methanesulfonyl chloride. The resulting solution is stirred for an additional 30 min and then quenched by adding 30 mL of ice-water. The organic layer is separated and washed successively with 1 M hydrochloric acid solution (30 mL), saturated aqueous sodium bicarbonate solution (30 mL), and brine (30 mL). The organic layer is dried over magnesium sulfate, filtered, and concentrated with a rotary evaporator to give 8.3–9.0 g (93–100%) of crude 4-hexyn-1-yl methanesulfonate which was used directly in the next step.

B. N-Benzyl-4-hexyn-1-amine. An oven-dried, 100-mL, one-necked, round-bottomed flask containing a magnetic stirring bar and a rubber septum inlet is flushed with argon and charged with 200 mg of sodium iodide. The crude mesylate 4-Hexyn-1-yl methanesulfonate, 40 mL of dimethyl sulfoxide and 10.9 g (102 mmol) of benzylamine are added via syringe. The resulting solution is heated in an oil bath at 47–53°C for 5 hr and then allowed to cool to room temperature. The reaction solution is poured into a separatory funnel containing 200 mL of aqueous 1% sodium hydroxide solution and the resulting mixture is extracted with ether (3 × 100 mL). The combined ether extracts are washed with brine (50 mL), dried over magnesium sulfate, filtered, and concentrated with a rotary evaporator. The residue (ca. 9 g) is purified by flash chromatography (ca. 300 g of silica gel using 1:1 hexane-ether containing 5% triethylamine as the eluent) to give 7.2–7.5 g (75–79% overall) of N-Benzyl-4-hexyn-1-amine as a colorless liquid.

C. (E)-1-Benzyl-3-(1-iodoethylidene)piperidine. A 250-mL, one-necked, round-bottomed flask containing a magnetic stirring bar and a reflux condenser topped with a rubber septum inlet is flushed with argon and charged with 4.0 g (21 mmol) of alkynylamine N-Benzyl-4-hexyn-1-amine, 11 g (73 mmol) of sodium iodide, 35 mL of 37% w/w formaldehyde solution, 5.4 g (22 mmol) of camphorsulfonic acid monohydrate and 80 mL of water. The resulting mixture is heated at reflux under an argon atmosphere for 15 min and then allowed to cool to room temperature. This solution is made basic by adding 5 M aqueous potassium hydroxide solution and then poured into a separatory funnel where it is extracted with dichloromethane (3 × 50 mL). The combined organic layers are dried over sodium sulfate, filtered, and concentrated with a rotary evaporator. The resulting residue is purified by flash chromatography (ca. 150 g of silica gel, 1:1 hexane-ethyl ether containing 5% triethylamine as eluent) to give 5.4–6.2 g (79–90%) of (E)-1-Benzyl-3-(1-iodoethylidene)piperidine as a colorless oil.