Reaction #2507839

Reaction equation

chloroenal

NaOH

Phosphorus oxychloride

chloroenal

sodium hydrogen carbonate

1-(3-propoxy-5,6,7,8-tetrahydro-5,5,8,8,-tetramethylnaphthalen-2-yl)ethanone

→

6-ethynyl-1,1,4,4,-tetramethyl-7-propoxy-1,2,3,4-tetrahydronaphthalene

Yield 39.0%

Solvents

dioxane water

dioxane H2O

dimethyl formamide

brine

Conditions

Workup

1. 1
   workup.STIRRINGwas stirred for 12 hours
2. 2
   ExtractionEthyl acetate extraction
3. 3
   Otherafforded the crude product
4. 4
   workup.STIRRINGthe reaction mixture was stirred for 2 hours
5. 5
   Otherto yield an orange reaction solution
6. 6
   TemperatureThe reaction solution was cooled to room temperature
7. 7
   Extractionextracted with EtOAc
8. 8
   DryingThe organic phase was dried (MgSO4)
9. 9
   Filtrationfiltered
10. 10
    Concentrationconcentrated
11. 11
    Otherto afford an orange oil which
12. 12
    Otherwas purified by radial chromatography (10:1 hexane:ethyl acetate)

Procedure

Phosphorus oxychloride (0.234 grams, 0.142 ml, 1.52 mmol) was added dropwise to dimethyl formamide (DMF) (4 ml) at room temperature under a nitrogen atmosphere. The solution was stirred for 30 minutes. The 1-(3-propoxy-5,6,7,8-tetrahydro-5,5,8,8,-tetramethylnaphthalen-2-yl)ethanone was added quickly (in one portion) to the orange solution, the reaction solution was heated to 60° C. and was stirred for 12 hours. The obtained dark brown solution was poured into ice water and the aqueous layer was adjusted to pH 7 with solid sodium hydrogen carbonate. Ethyl acetate extraction afforded the crude product, the chloroenal (6-[1-hydroxy,2-chloro-ethenyl]-1,1,4,4-tetramethyl-7-propoxy-1,2,3,4-tetrahydronaphthalene), 0.128 grams, as an orange/brown oil. A solution of the crude chloroenal in dioxane:water (3:2; 5 ml) was added to a solution of NaOH (0.061 grams, 1.52 mmol) in dioxane: H2O (3:2; 20 ml), at 80° C., and the reaction mixture was stirred for 2 hours, to yield an orange reaction solution. The reaction solution was cooled to room temperature, poured into brine and extracted with EtOAc. The organic phase was dried (MgSO4), filtered, and concentrated to afford an orange oil which was purified by radial chromatography (10:1 hexane:ethyl acetate) to give the product 6-ethynyl-1,1,4,4,-tetramethyl-7-propoxy-1,2,3,4-tetrahydronaphthalene (39%) as a yellow oil [1H-NMR (400 MHz, CDCl3): d 7.38(s, 1H, Ar—H), 6.76(s,1H, Ar—H), 3.98 (t, J=6.6 Hz, 2H, OCH3), 3.19 (s, 1H, CH),1.83 (m, 2H, CH2),1.66 (m, 2H, 2CH2),1.26 (s, 6H, 2CH3),1.23 (s, 6H, 2CH3), 0.93 (t, J=7.4 Hz, 3H, CH3)].

Source