1- Bromo-2,2-dimethoxypropane

A. 1 -Bromo-3,3-dimethoxypropane (Note 2). Into a flame-dried, fared, 1-L, round-bottomed flask containing 500 mL of methylene chloride (CH2CI2) (Note 3) at 0°C is bubbled anhydrous hydrogen bromide for approximately 15 min (33.0 g, 0.408 mol of HBr absorbed) (Notes 4,5). Acrolein (22.9 g, 27.2 mL, 0.408 mol) is added rapidly (30 sec) via syringe to the stirred solution (Note 6). After 2 min, a solution of 86.6 g (89.3 mL, 0.816 mol) of trimethyl orthoformate (Note 7) in methanol (100 mL) is introduced into the reaction mixture via cannula over 5 min. The reaction mixture is stirred for 10 min at 0°C, and solid anhydrous calcium carbonate (12.0 g, 0.120 mol) is then added in one portion. The reaction mixture is stirred for an additional 1 hr, the solution is filtered, and the filtrate concentrated under reduced pressure to ca. 50 mL. The residue is distilled through a 25-cm Vigreux column under reduced pressure to give, after a forerun of variable amount (-10 mL) (Note 8), 38.8 g (52%) of 1-bromo-3,3-dimethoxypropane as a colorless liquid, bp 67-69°C at 24 mm (Note 9). 

Bromo-3,3-dimethoxypropane Propane, 3-bromo-1,1-dimethoxy- (9) (36255-44-4) Acrolein (8) 2-Propenal (9) (107-02-8)... 

The checkers found that commercially available 3-bromo-1,1-dimethoxypropane (Aldrich Chemical Company, Inc.) was unsatisfactory, even after purification, for preparation of the stannane in part B, resulting in greatly diminished yields. 

Bromo-3-chloro-2,2-dimethoxypropane 2-Propanone, l-bromo-3-chloro-,... 

The condensation of 2-(5-bromo-4-chloro-2-hydroxybenzoyl)pyridine 506 in a sealed tube with ammonia and acetone proved a convenient route to 2//-l,3-benzoxazine derivative 225 via the imine intermediate 507 <1996CPB734>. The yield was improved considerably and a closed vessel was not required for the reaction when the ammonia was prepared in situ from NH4I and piperidine, and 2,2-dimethoxypropane was used instead of acetone (Scheme 95). The improved method was extended to the preparation of other 2,2-disubstituted-2//-l,3-benzoxazine derivatives <2001T7501>. 

Bromo-2-butene (cis and trans mixture) 2-Butene, 2-bromo- (13294-71-8), 65, 42 1 -Bromo-3-chloro-2,2-dimethoxypropane 2-Propanone, 1 -bromo-3-chloro-,... 

A. 2-( Bromomethyl)- .-( ehloromethyD-1, -dioxane. A 100-mL, round-bottomed flask is equipped with a 10-mL Dean-Stark apparatus and a condenser. The flask is charged with 30.0 g (0.138 mol) of l-bromo-3-chloro-2,2-dimethoxypropane (Note 1), 10.0 mL (0.138 mol) of 1,3-propanediol (Note 2), and 3 drops of concentrated sulfuric acid. The resulting solution is heated (bath temperature 140°C) for 8 hr (Note 3) with distillative removal of methanol (ca. 11 mL). The mixture is allowed to cool to room temperature and the crude product is partitioned in 150 mL of pentane and 40 mL of water. The... 

Dimethoxycyclopropene (3). Baucom and Butler have reported a relatively simple synthesis of 3,3-dimethoxycyclopropcne (3) from 2,3-dichloropropene (1). This compound is converted into l-bromo-3-chloro-2,2-dimethoxypropane (2) by treatment... 

PreparationThe reagent is available by two different routes. It can be obtained in about 50% yield by the reaction of 2-methoxypropene2 and NBS in CC14 (method A) or by pyrolysis of l-bromo-2,2-dimethoxypropane (available from bromoacetone). The reagent (neat) decomposes at room temperature and is best stored in the dark as... 

The reaction of l-bromo-3-chloro-2,2-dimethoxypropane with potassium amide in liquid ammonia at — 50 C provides an efficient route to 3,3-dimethoxycyclopropene (1). ... 

Scheme 7.3 Synthesis of C-labeled patulin. Reagents and conditions a) HCl, MeOH, 64% b) dimethoxypropane, H2SO4, acetone, rt, 24 h, quant c) PCC, CH2CI2, rt, 23% d) ethyl bromo...

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