2-(2,5-dimethoxyphenyl)-1,3-dioxane

Procedure

To 2,5-dimethoxybenzaldehyde (1.0 g, 6.02 mmol) in 1,3-propanediol (1.75 mL, 24.2 mmol, 4 eq.) were added (MeO)₃CH (0.75 mL, 6.86 mmol, 1.1 eq.) andBu₄N.Br₃ (26 mg, 0.05 mmol, 0.01 eq.). After stirring at room temperature for 45 min the reaction was quenched with saturated NaHCO₃ (5 mL) and H₂O (20 mL). The mixture was then extracted with EtOAc (3 × 10 mL) and the combined organic fractions washed sequentially with 10% NaHCO₃ (20 mL), H₂O (4 × 20 mL) then dried (MgSO₄) and concentrated in vacuo to give 2-(2,5-dimethoxyphenyl)-1,3-dioxane (1.35 g, 100%) as a colourless oil suitable for further use.

2-(2,5-dimethoxyphenyl)-1,3-dioxane:

¹H NMR (500 MHz, CDCl₃): δ = 1.41-1.45 (m, 1H), 2.21-2.28 (m, 1H), 3.79 (s, 3H), 3.80 (s, 3H), 3.98-4.04 (m, 2H), 4.24-4.27 (m, 2H), 5.85 (s, 1H), 6.81 (d, J = 8.9 Hz, 1H), 6.85 (dd, J = 8.9 and 3.1 Hz, 1H), 7.20 (d, J = 3.1 Hz, 1H).

¹³C NMR (125 MHz, CDCl₃): δ = 25.9, 55.8, 56.4, 67.6, 96.8, 111.9, 112.3, 115.9, 127.7, 150.6, 153.9.

2-(3,4-dimethoxyphenyl)-1,3-dioxane:

¹H NMR (500 MHz, CDCl₃): δ = 1.43-1.46 (m, 1H), 2.19-2.27 (m, 1H), 3.87 (s, 3H), 3.91 (s, 3H), 3.96-4.01 (m, 2H), 4.25-4.28 (m, 2H), 5.46 (s, 1H), 6.85 (d, J = 8.0 Hz, 1H), 7.01 (dd, J = 8.0 and 2.0 Hz, 1H), 7.05 (d, J = 2.0 Hz, 1H).

Gopinath, R.; Haque, S. J.; Patel, B. K. J. Org. Chem., 2002, 67, 5842-5845. DOI: 10.1021/jo025701o

Acyclic and cyclic acetals of various carbonyl compounds were obtained in excellent yields under a mild reaction condition in the presence of trialkyl orthoformate and a catalytic amount of tetrabutylammonium tribromide (TBATB) in absolute alcohol. Chemoselective acetalization of an aldehyde in the presence of ketone, unsymmetrical acetal formation, shorter reaction times, mild reaction conditions, the stability of acid-sensitive protecting groups, high efficiencies, facile isolation of the desired products, and the catalytic nature of the reagent make the present methodology a practical alternative.

 http://pubs.acs.org/doi/abs/10.1021/jo025701o

Scheme 1.  Proposed Mechanism of Acetalization

Other References

1. Wuts P. G. M.; Greene, T. W. "Greene's protective groups in organic synthesis", 4th Edition, 2007, John Wiley & Sons, Inc.

2. Donner, C. D. Synthesis, 2010, 415-420. DOI: 10.1055/s-0029-1217118

3. Tan, N. P. H.; Donner, C. D. Tetrahedron Lett., 2008, 49, 4160-4162. DOI: 10.1016/j.tetlet.2008.04.112




A TOUR


 JUNNAR, MAHARASHTRA INDIA
http://en.wikipedia.org/wiki/Junnar



 

Junnar जुन्नर
city
Junnar Location in Maharashtra, India
Coordinates: 19.2°N 73.88°ECoordinates: 19.2°N 73.88°E
Country	India
State	Maharashtra
District	Pune
Elevation	689 m (2,260 ft)
Population (2001)
• Total	24,456
Languages
• Official	Marathi
Time zone	IST (UTC+5:30)
Website	[1]

 .
Lenyadri Caves

 
 Naneghat caves near Junnar

Shivneri fort

 

 
 

 

 


 







 




Kukdeshwar temple at Pur- Junnar, Dist. Pune. Small shrine in the vicinity



 

Richly stone carved Buddhist caves on mountain at Lenyadri ; Ganesh Gufa ; Ashtavinayak ; Taluka



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