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
http://pubs.acs.org/doi/abs/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.
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
.
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
GANESH GATE
A TOUR
JUNNAR, MAHARASHTRA INDIA
http://en.wikipedia.org/wiki/Junnar
| Junnar जुन्नर |
|
|---|---|
| city | |
Junnar
|
|
| 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
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
GANESH GATE
.
.
.
