Study On The Synthesis Of Citronellyl Oxyacetaldehyde From Citronellal

Citronellal oil containing citronellal as its main component is a rich natural resource in China.A series of important perfumes such as citronellyl oxyacetaldehyde has been synthesized from citronellal.Citronellyl oxyacetaldehyde with thick and intense rose and lily note is widely used for waking up floral essences and a extremely precious synthetic perfume with wide applied perspective.However, the detailed research to prepare it from natural materials is not reported so far. By referring to many previous literatures concerned and using phase transfer catalysis technology and so on,we had synthesized citronellyl oxyacetaldehyde from citronellal as a starting material by way of citronellol and citronellyl oxyacetaldehyde diethyl acetal. The reaction course was studied in detail and we obtain better results.The synthetic principle of citz-onellyl oxyacetaldehyde is as follows:bei~rO~$~ìa.iao~ DraI2ofoc2H5)2COC~CH(OC.H~CH~OC~CHO1.By using diethylene glycol dimethyl ether (DGDE) as phase transfer catalyst (PTC) and water and benzene as mixed solvent,we studied the reduction reaction of citronella] with NaBH4 and citronellol was prepared under the optimum reaction conditions obtained by orthogonal experiment:molar ratio of citronellal to NaBH4 to DGDE was 1:O.6:O.l,the volume of benzene and water was 12m1 and 2Oml respectively, reaction temperature was 40C,reaction tine was 2.5h(based on O.2mol of citronella]). The overall yield and the purity of citronellol were 94.7% and 95. 1% respectively.2.O-alkylation reaction of citronellol with bromoacetaldehyde diethyl acetal was also studied in detail.Citronellyl oxyacetaldehyde diethyl acetal(CODA) was synthesized with two methods. (1)By using PEG-400 as PTC and solid powdered NaQH as base, citronellyl oxyacetaldehyde diehtyl acetal was prepared under the optimum conditions secured by orthogonal experiment:molar ratio of citronellol to3bromoacetaldehyde diethyl acetai to NaOfI to PEG-400 was 1:1.2:3:0. 05, reaction time was 15h, reaction temperature was 100tZ (based on 0.05 mci of citroneLlol and 35m1 of dry toluene) .The overall yield and the purity of CODA were 88.3%and 95.8% respectively. (2)By using KF-AL203(Ando catalyst)as catalyst and acetonitrile as solvent, CODA was synthesized under the optimum conditions obtained by orthogonal experiment:molar ratio of citronellol to bromoacetaldehyde diethyl acetal was 1:1. 2. mass of KF-AL2O3was 8g. reaction temperature was 60C, reaction time was 8h (based on 0. 05.ol of citronellol and 30m1 of acetonitrile). The overall yield and the purity of CODA were 87.8% and 95.2% respectively.3.citronellyl oxyacetaldehyde was synthesized by hydrolytic reaction under the optimum conditions obtained by orthogonal experiment:on the basis of 0.02nd of CODA, the concentration of citric acid was 15%, reaction time of reflux was lh.The overall yield and the purity of citronel.lyl oxyacetaldehyde reached 78. 5% and 96. 5% respectively.All the products were characterized by IR or 'HNMRThere are some original methods in the preparation of citronellol from citronellal by using DGDE as PTC,NaBIl4as reducing agent, water and benzene as mixed solvent,and in the O-alkylation reaction of citronellol with bromoacetaldehyde diethyL acetal by using PEG-400 as PTC, solid powdered NaOH as base and then using KF-AL203 as catalyst. So far these improved methods have not been reported yet.The experimental result indicates that the novel synthesis of citronellyl oxyacetaldehyde from citronellal is an effective improvement and has significant advantages when compared with the traditional method:the simple operation, the mild reaction condition, the shortened reaction time, the economical work, the reduced price, the good yield and the less pollution. It can be expected that the method will bring about better producing perspective.