Propargyl thiocyanate

Apparatus 3-1 round-bottomed flask with a wide neck. 

A suspension of sodium amide in 500 ml of anhydrous liquid artmonia was prepared from 18 g of sodium (see Chapter II, Exp. 11). To the suspension was added in 10 min with swirling a mixture of 0.30 mol of 1-chloro-l-ethynylcyclohexane (see VIII-2, Exp. 27) and 50 ml of diethyl ether. The reaction was very vigorous and a thick suspension was formed. The greater part of the ammonia was evaporated by placing the flask in a water bath at 50°C. After addition of 500 ml of ice-water the product was extracted three times with diethyl ether. The ethereal extracts were dried over anhydrous KjCOj and subsequently concentrated in a water-pum vacuum. Distillation of the residue afforded the amine, b.p. 54°C/15 mmHg, n 1.4345, in 87% yield. 

Apparatus 1-1 three-necked, round-bottoned flask, provided with a dropping funnel, a mechanical stirrer and a thermometer, combined with a vent. 

Apparatus. 2-1 three-necked, round-bottomed flask, provided with a gas inlet tube, a gas-tight mechanical stirrer and a gas outlet two washing bottles filled with paraffin oil were connected with the gas inlet and outlet. 

To a suspension of 2.0 mol of finely powdered 2-butyne-l,4-d1ol (note 1) in 600 ml of dry dichloromethane were added 50 g of anhydrous p-toluenesulfon1c acid (note 2). Isobutene (6 mol) was introduced with vigorous stirring. The flow was adjusted in such a way that only a small amount escaped from the solution (note 3). The reaction was slightly exothermic, so that no external cooling was applied. 

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The highly reactive 2-azadiene with an allene and heterocumulene structure 126, prepared by gas-phase thermolysis of propargyl thiocyanate, has been found by the Banert group to be an efficient precursor for thiazole derivatives by nucleophilic-induced heteroannulation through carbon and... 

A mixture of 0.40 mol of potassium thiocyanate, 45 ml of water and 0.30 mol of propargyl bromide was vigorously stirred for 30 min at 80 C. After cooling, the product was extracted with diethyl ether. Drying of the extract of magnesium sulfate, followed by distillation in a water-pump vacuum, gave propargyl thiocyanate. 

Recently, the solvolyses of l-chloro-l,3,3-triarylallenes 10 (andof 1-butyl-3,3-diphenyl-allenyl chloride) were carried out in the presence of thiocyanate and o-ethyl dithiocar-bonate anions as nucleophiles and found to give the corresponding allenyl derivatives 11 and 12 in good yield (equation 3)18. However, when potassium cyanate was used as a nucleophile, the cyanate ion attacked at the /-position to give the propargyl amines 14 after decarboxylation of the unstable intermediate 13 (equation 4). 

Several other propargylic substrates have successfully undergone [3,3]-sigmatropic rearrangements. Examples are thiocyanates to isothiocyanates [580], the opposite conversion [581] and the equilibrium between such species as exemplified by 173 (Scheme 1.77) [582], cyanates to isocyanates [582] and the formation of isoselenocya-nates [583] and azides [584]. 

Probably the most convenient laboratory preparation of isothiazole was devised by Wille and his collaborators34 (Scheme 11) and depends on the cyclization with liquid ammonia of the cis-addition product from propargyl aldehyde and sodium thiosulfate or thiocyanate.34, 35... 

Phenyl-3-methyl-5-pyrazolone N-Phenyl-p-phenylenediamine Phosgene Phthalic anhydride Pivalyl indandione Potassium thiocyanate Propargyl alcohol n-Propyl bromide n-Propyl isocyanate Pyrogallol... 

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