Ethanone, 1-(3,4-dihydro-2H-pyrrol-5-yl)- (9CI)

Yellow to Orange Liquid

It is isolated from rice and identified as the compound responsible for the flavor and aroma of scented rice after cooking.

ChEBI: 2-acetyl-1-pyrroline is a pyrroline that is 1-pyrroline in which the hydrogen at position 2 is replaced by an acetyl group. It is an aroma and flavour compound present in jasmine rice and basmati rice. It is responsible for the 'popcorn' aroma in a large variety of cereal and food products. It is one of the key odourants of the crust of bread and considered to be responsible for the cracker-like odour properties. In bread, it is primarily generated during baking but amounts are influenced by ingredient composition and fermentation conditions. It has a role as a metabolite, a flavouring agent and a Maillard reaction product. It is a methyl ketone, a pyrroline and an acylimine.

Method for the synthesis of 2-acetyl-1-pyrroline, comprising the steps of:

1) dissolving pyrrolidine-2-carbonitrile hydrochloride in an inorganic alkaline solution for neutralization reaction, carrying out several extractions with an organic extractant, combining the organic layers, and then drying and dehydrating by adding a drying agent to the organic layer, filtering, and then removing the volatile components in the filtrate, to obtain an intermediate product; said pyrrolidine-2-carbonitrile hydrochloride being (S)-pyrrolidine-2-carbonitrile hydrochloride or (R)-pyrrolidine 2-carbonitrile hydrochloride or a mixture of the two isomers of (S)-pyrrolidine-2-carbonitrile hydrochloride and (R)-pyrrolidine-2-carbonitrile hydrochloride in any ratio; i.e., the starting material is an S-configurational feedstock or an R-configurational feedstock or a mixture of an S-configurational feedstock and an R-configurational feedstock in any ratio.

Said inorganic alkaline solution is at least one of potassium carbonate solution, potassium bicarbonate solution, sodium carbonate solution, sodium bicarbonate solution; the concentration of the alkaline solution is 10-50 wt%.

2) dissolve the intermediate product obtained in the previous step in an organic solvent, dropwise add tert-butyl hypochlorite to carry out a halogenation reaction, and then add potassium tert-butanol to carry out an elimination reaction, filter, and then remove the volatile components in the filtrate to obtain pyrrolidine-2-carbonitrile;

3) dissolve pyrrolidine-2-carbonitrile in an organic solvent, add Grignard reagent to carry out Grignard reaction, then add acid solution to carry out hydrolysis, and then carry out several times of extraction with an organic extractant, merge the organic layer, and then add a drying agent to dry and dehydrate to the organic layer, filter, and then remove the volatile components in the filtrate, and obtain the product.