Benzodioxepines

H- 1,5-Benzodioxepin, 3,4-dihydro-synthesis, 7, 622 5H-l,4-Benzodioxepinediones synthesis, 7, 622 5H-l,4-Benzodioxepinones synthesis, 7, 622 lH-2,3-Benzodioxepins synthesis, 7, 620 3H-2,4-Benzodioxepins synthesis, 7, 621... 

Recent results by St-Jacques and collaborators (45) have revealed that the ring conformation in 2,4-benzodioxepin which can be the chair 39 (Fig. 8), the twist boat 40 or the boat form 1, was determined by the nature of substitution. A chair (39) with a minor amount of the twist-boat (40) was observed for the non substituted compound 42, whereas the chair form was found for the methyl derivative 43 and the twist boat-form for the dialkyl derivatives 44, 45, and 46. 

Protection of /C=0. This diol (1) reacts sluggishly with carbonyl compounds under acid catalysis, but the orthoformate 2,3-methoxy-l,5-dihydro-3//-2,4-benzodioxepine, derived from 1, reacts to form 2,4-benzodioxepines (3). The car-... 

B. 3-Vinyl-l,5-dihydro-3H-2,4-benzodioxepine. An oven-dried, 2-L, threenecked, round-bottomed flask is equipped with a magnetic stirring bar. a calcium chloride drying tube, and two rubber septa. The flask is charged with 41.45 g (0.3 mol) of 1,2-benzenedimethanol, 5.71 g (0.03 mol) of p-toluenesulfonic acid monohydrate (Note 1), and 600 mL of dry 1,2-dimethoxyethane (Notes 1 and 7). Stirring is initiated, and 49.2 mL (0.45 mol) of trimethyl orthoformate (Note 1) and 30.1 mL (0.45 mol) of acrolein (Note 1) are then added sequentially via syringe. The reaction mixture is... 

S)-1,2-dihydroxyethyl)]-1,5-dihydro-3H-2,4-benzodioxepine is determined by HPLC analysis of the derived bis-Mosher ester to be 84% (Note 16). 

The mother liquor is then concentrated to afford 2.4 g of a brown yellow liquid (Note 22). Flash chromatography of this material on 30 g of Si02 with elution by EtOAc then by EtOAc MeOH (5 1 v/v) affords 0.63 g (2%) of 3-[(lS)-1,2-dihydroxyethyl)]-1,5-dihydro-3H-2,4-benzodioxepine and 0.69 g (92% recovery) of dihydroquinidine 9-0-(9 -phenanthryl) ether. 

The reaction mixture was monitored by TLC analysis on silica gel (4 1 EtOAc hexane v/v). 3-Methoxy-1,5-dihydro-3H-2,4-benzodioxepine (R = 0.5) is first produced by transesterification with trimethyl orthoformate, and is then transformed to the final product (R = 0.6). 

The oil contained 5-10% t-BuOH by weight. 3-[(1 R)-1,2-Dihydroxyethyl)]-1,5-dihydro-3H-2,4-benzodioxepine was produced with 84% ee when dihydroquinine-... 

Of the three types of racemates,11 conglomerate, racemic compound, and solid solution, 3-(1,2-dihydroxyethyl)-1,5-dihydro-3H-2,4-benzodioxepine shows melting point behavior characteristic of a racemic compound. The racemic diol is much higher melting than the enantiomerically enriched diol as shown in the Figure 1. Therefore the diol of lower ee precipitates first during recrystallization and the enantiomerically enriched diol remains in the mother liquor. High ee diol (97% ee) is then obtained upon recrystallization of this mother liquor. 

Vinyl-1,5-dihydro-3H-2,4-benzodioxepine 2,4-Benzodioxepin, 3-ethyl-1,5-dihydro-(13) (142169-23-1)... 

This collection begins with a series of three procedures illustrating important new methods for preparation of enantiomerically pure substances via asymmetric catalysis. The preparation of 3-[(1S)-1,2-DIHYDROXYETHYL]-1,5-DIHYDRO-3H-2.4-BENZODIOXEPINE describes, in detail, the use of dihydroquinidine 9-0-(9 -phenanthryl) ether as a chiral ligand in the asymmetric dihydroxylation reaction which is broadly applicable for the preparation of chiral dlols from monosubstituted olefins. The product, an acetal of (S)-glyceralcfehyde, is itself a potentially valuable synthetic intermediate. The assembly of a chiral rhodium catalyst from methyl 2-pyrrolidone 5(R)-carboxylate and its use in the intramolecular asymmetric cyclopropanation of an allyl diazoacetate is illustrated in the preparation of (1R.5S)-()-6,6-DIMETHYL-3-OXABICYCLO[3.1. OJHEXAN-2-ONE. Another important general method for asymmetric synthesis involves the desymmetrization of bifunctional meso compounds as is described for the enantioselective enzymatic hydrolysis of cis-3,5-diacetoxycyclopentene to (1R,4S)-(+)-4-HYDROXY-2-CYCLOPENTENYL ACETATE. This intermediate is especially valuable as a precursor of both antipodes (4R) (+)- and (4S)-(-)-tert-BUTYLDIMETHYLSILOXY-2-CYCLOPENTEN-1-ONE, important intermediates in the synthesis of enantiomerically pure prostanoid derivatives and other classes of natural substances, whose preparation is detailed in accompanying procedures. 

Cyclopropan-(l-spiro-3)-l,5-dihydro-2,4-benzodioxepin 2-Methoxy-carbonyl- E19b, 1140... 

Dihydro-3//-2,4-benzodioxepin, 472 7,7-Dimethyl-l,2,4-trioxepane, 472 3,3-Dialkyl-6-(l-phenylvinyl)-l,2,4-trioxane, 473... 

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