Such cyclic monoethers as rose oxide and linalool oxide are known to possess floral note, but to our knowledge, organoleptic properties of cyclic diethers are unknown. In the course of our work on acid-catalyzed aldol- condensation of alkyl cyclohexanones with formaldehyde, two ethyl esters of 6-oxohexanoic acids having 1, 3-dioxane moiety, i. e., ethyl 5- (4- oxobutyl) -1, 3- dioxane-5- carboxylate (4) and ethyl 4- (5-formyl-1, 3-dioxan-5-yl) butyrate (5), and their derivatives were prepared to know their odor.
These ethyl esters 4 and 5 were synthesized by oxidation with lead tetraacetate of 2, 4-dioxaspiro [5.5] undecan- 7- one The first oxidation was carried out in acetic acid to give acetoxy ketone 1. Hydrolysis of 1 gave a tautomeric mixture of a-hydroxy ketones (2 and 3) which could not be separated by GLC or elution chromatography. The hydrolyzed products (2 and 3) were subjected to the second oxidation in benzene-ethanol to afford a mixture of the ethyl esters 4 and 5 by cleavage of the cyclohexane ring with relative ratio of 1 : 24.
The ethyl esters (4 and 5) were changed to acetals 7 and 8. The ethyl ester 5 was convered to 4- (5-formyl-1, 3-dioxan-5-yl) butyric acid 6, ethyl 4- (5 - hydroxymethyl-1, 3-dioxan-5-yl) butyrate 9 (50.6 % yield), and ethyl 4- [5- (1-hydroxyethyl) -1, 3-dioxan-5-yl] butyrate 10 (52.5 % yield) by treating with alkali, with lithium aluminum hydride, and with methylmagnesium iodide, respectively.
In addition, the ethyl ester 5 was heated with 2- (6, 6-dimethyl-2-norpinen-2-yl) ethyl alcohol (nopol) in the presence of sodium to afford nopyl esters of 4- (5- formyl-1, 3-dioxan- 5- yl) butyric acid 11, 4- (1, 3-dioxan-5-yl) butyric acid 12, and 2, 4-dioxaspiro [5. 4] dec-7-ene-8-carboxylic acid 13 in 18 %, 5 % and 6 % yield. The compound 12 is a decarboxylated product. The reaction of 5 with sodium gave ethyl esters 14 and 15, and 5 was gradually changed to 14 on standing at room temperature.
抄録全体を表示