Stark s. Dean

Stannyl hydrides s. Tin hydrides, organo-Stark s. Dean Statistics, mathematical, optimization by - 13, 696 suppl. 27 Stereodiemistry... 

A mixture of 4.2 g (40.7 niniol) of (S)-valinol, 4.4 g (41 mmol) of benzaldeliyde and 100 mL of benzene is refluxed for 3 h using a Dean-Stark trap. After concentrating under reduced pressure tlie residue is allowed to stand at r.t. to give crystals of 2a. Rccrystallization from pentane provides colorless prisms yield 6.8 g (89%) mp 71-72 C. 

The synthesis of functionahzed tetrahydrocarbazoles can be promoted by microwave irradiation [84], The organocatalytic four-component reaction of a solution of 2-substituted indole, aromatic aldehyde (2 equiv) and Mel-drum s acid in benzene in the presence of DL-proline proceeds when heated under Dean-Stark conditions for 5 min in a single-mode microwave reactor to give the tetrahydrocarbazole product as a mixture of diastereoisomers (Scheme 24). 

By heating 2-benzyloxycyclohexanone 208 and (R)-l-phenylethylamine in refluxing toluene for 4 days in a Dean-Stark apparatus, the imine 209 was formed, then a rearrangement occurred to give first the a-aminocyclohexanone derivative 210 and finally the Q, o -disubstituted imine 211 with moderate diastereoselectivity. Reduction of this imine with sodium borohydride gave a mixture of two trans diamines (S,S)-212 and (R,R)-212, which were separated by chromatography. The enantiomers of 1-benzyl-1,2-diaminocyclohexanes 213 were then obtained by hydrogenolysis [99] (Scheme 31). 

The reaction of (.S )-tryptophanol 236 with dicarbonyl compound 237 under Dean-Stark conditions afforded the bicyclic lactam 238, as a mixture of diastereomers. Exposure to acid of this mixture gave the indolo[2,3- ]quino-lizidine 239 in excellent yield, as a single diastereomer (Scheme 46). This chemistry was subsequently applied to... 

Lithiimi iodide dihydrate is available from Fluka A.G., Buchs, S.G., Switzerland. The checkers used the trihydrate and, by means of a Dean Stark trap attached between the flask and the condenser, 1 mole, of water was removed via azeotropic distillation with collidine. 

In a system containing a Dean Stark trap arranged for azeotropic removal of water. 9.3 g (56 mmol) of (-)-(S)-a-(mcthoxymethyl)benzeneethanamine and 6.5 g (66 mmol) of cyclohexanone arc dissolved in 100 mL of benzene or toluene and heated to reflux until the theoretical amount of water is collected in the trap. Removal of the solvent and distillation of the oily residue gives a clear viscous oil yield 13.0 g (93 %) bp (Kugelrohr) 95-100°C/0.5 Torr [a]D —46.2 (c = 6.7, methanol). 

A. (i-Mdth -b -2-oclalone S -Dimethylhydrawne. A 250-ml., round-bottomed flask equipped with a magnetic stirring bar and a Dean-Stark water separator is maintained under a dry nitrogen atmosphere (Note 1) and eharged with 7.4 g. (0.045 mole) of 10-methyl-A < -2-octalone [2(3 f)-Naphthalenone, 4,4a,5,6,7,8-hexahydro-4a-methyl-] (Note 2), 9.0 g. (0.15 mole) of N,N-dimethylhydrazine, 150 ml. of dry benzene, and 0.02 g. of p-toluenesulfonic acid. This mixture is refluxed for 10-14 hours, after which time no further water separates. Benzene and excess N,N-dimethylhydrazine are then removed by simple distillation, and the residue is distilled under reduced pressure to give 8.1 g. (87%) of the dimethylhydrazone as a pale-yellow liquid, b.p. 94-98° (0.2 mm.) (Notes 3, 4). 

Anisole [100-66-3] M 108.1, f.p. -37.5", b 43"/l 1mm, 153.8"/760mm, d 5 0.9988, n s 1.5143. Shaken with half volume of 2M NaOH, and emulsion allowed to separate. Repeated 3 times, then washed twice with water, dried over CaCl2, filtered, dried over sodium wire and finally distd from fresh sodium under N2, using a Dean-Stark trap, samples in the trap being rejected until free from turbidity [Caldin, Parbov, Walker and Wilson JCSFT1 72 1856 1976. ... 

S. (-)-(Camphorsulfonyl)imine. A 1 -L, round-bottomed flask is equipped with a two-inch egg-shaped magnetic stirring bar, a Dean-Stark water separator, and a double-walled condenser containing a mineral oil bubbler connected to an inert gas source. Into the flask are placed 5 g of Amberylst 15 ion exchange resin (Note 4) and 41.5 g of the crude (+)-(1 S)-camphorsulfonamide in 500 mL of toluene. The reaction mixture is heated at reflux for 4 hr. After the reaction flask is cooled, but while it is still warm (40-50°C), 200 mL of methylene chloride is slowly added to dissolve any (camphorsulfonyl)imine that crystallizes. The solution is filtered through a 150-mL sintered glass funnel of coarse porosity and the reaction flask and filter funnel are washed with an additional 75 mL of methylene chloride. 

A. 6-Bramo-S,4-dimethoxybenzaldehyde cyclohexylimine (1). A 2-L, threenecked flask is equipped with a Dean-Stark trap, reflux condenser, magnetic stirrer, and nitrogen inlet. The vessel is purged with nitrogen and charged with 40,0 g (0.16 mol) of 6-bromo-3,4-dimethoxybenzaldehyde (6-bromo-veratraldehyde) (Note 1), 22.4 mL (0.20 mol) of cyclohexylamine (Note 2), and 800 nt of toluene. The mixture is refluxed for 16 hr (Note 3). The solution is cooled to room temperature and the solvent is removed on a rotary evaporator. The residual crystalline mass is recrystallized from a 3 1 hexane-methylene chloride mixture (1.5 L) to provide 48.4-51.4 g of the imlne 1 as white crystals In two crops (mp 172-172.5°C)2 (Note 4). 

A. S-fBromomethyD-Z-fahloromethyD-l, 3-dioxane A 100-mL, round-bottomed flask 1s equipped with a 10-mL Dean-Stark apparatus and a condenser. The flask 1s 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... 

Tetrahedral models (U-1), 1262-1264 Wash bottle, polyethylene (S-4), 1111 Water pump, plastic, 25 Water separators, Oarke-Rahrs methyl ester column, 1172 Dean-Stark (L-2), 617 Wide-blade spatula (I-l), 493... 

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