Borane, dimethoxy

Hoffmann et al have reported the addition of allyl(dimethoxy)borane to linear and branched a-aryl-aldimines (entries 16-19, Table 2). The absence of a-deprotonation may be explained by a delicate balance between the basicity and the reactivity of the allylboronate. Allyl(dimethoxy)borane should thus be considered the reagent of choice in reactions with enolizable aldimines. Reactions are conveniently carried out at 25 °C in CH2CI2 and work-up is performed using triethanolamine to break up amine-boronate complexes. Allyl(dimethoxy)borane also adds to the cyclic imine, A -piperideine, in 90% yield. The reported yields for the addition of allyllithium and allylmagnesium chloride to A -piperideine are low. 

D-Lyxose, treated with ethyl(dimethoxy)borane in the presence of acid, gave the glycoside ester (3) from which methyl a-D-lyxofuranoside was obtained in 80% yield. In related fashion methyl a-D-mannofuranoside was obtained in similar yield. Alternatively, a wide range of 3-D-lyxofuranosides can be made by way of the 5-O-acetyl-a-glycofuranosyl bromide of (3). ... 

A study of the stability of compounds derived from D-glucose and D-fructose with boric acid or phenylboronic acid has found that the stability constants for the fructose compounds are much greater than those for the glucose compounds. The synthesis of crystalline 3-0-acetyl-2,4-0-phenylboranediyl- -D-ribopyranosyl bromide in a two pot process from D-ribose has been described along with some of its selective glycosylation reactions. Ethyl (dimethoxy)borane has been used in the synthesis of anomerically pure furanosides from the free sugars. Thus methyl 2,3-0-ethylboranediyl-tt-D-lyxofuranoside was prepared and then de-esterified under essentially neutral conditions to the glycoside in 80%... 

The regiochemistry of the electrophilic attack of the pentadi-enylpotassium species is related to the nature of the electrophile and the substitution pattern of the dienyl system. In general, halotrialkylsilanes, fluoro(dimethoxy)borane, and chlorotri (isopropoxy)titanium preferentially attack the terminal position. 

Non-aromatic Boron Heterocyclics.—The range of cyclic dialkoxyboranes derived from monosaccharides has been extended to cover deoxyaldohexoses [by treatment of the sugar with ethyl(dimethoxy)borane] and derivatives of glucose (by a novel reduction process). If two dioxaborolane units are appropriately disposed in space, exchange of alkoxy groups between boron atoms is possible, as for example in the equilibration of compounds (17) and (18). ... 

Benzoxazole reagieren mit Diboran in 1,2-Dimethoxy-athan bei 25° unter Amin-Boran-Bildung, nachfolgender Umlagerung und Verseifung der 2,3-Dihydro-(benzo-1,3,2-oxazaborole), mit Salzsaure zu den entsprechenden o-Amino-phenolen2 ... 

Diboran reduziert Monocarbonsauren in THF oder 1,2-Dimethoxy-athan, mit dem Losungsmittel als Boran koordiniert, in zwei Schritten. Zuerst wird bei -20° schnell und quantitativ Triacyloxy-boran gebildet, im zweiten langsameren Schritt (25°, 1 Stde.) Trialkoxy-boroxol, das nach Hydrolyse den gewiinschten Alkohol liefert4. 

Mono(2,6-dimethoxybenzoyl)tartaric acid Butanedioic acid, 2-[(2,6-dimethoxybenzoyl)oxy-3-hydroxy-, [R-(R, R )]- (12) (116212-44-3) 2,6-Dimethoxybenzoic acid Benzoic acid, 2,6-dimethoxy- (8,9) (1466-76-8) Trifluoroadetic anhydride Acetic acid, tritluoro-, anhydride (8,9) (407-25-0) Borane-Tetrahydrofuran Furan, tetrahydro-, compd. with borane (1 1) (8,9) (14044-65-6)... 

Dimethoxy [ 1 -trimethy lsilyl-1,2-buta-dienyl]borane, 218 Triisopropoxy[l-(trimethylsilyl)-l,2-butadienyl]titanium, 218 Vinyl groups... 

Dibromoborane-Dimethyl sulfide, 92 Dichloro(dimethylamino)borane, 120 Diisobutylaluminum hydride-Boron trifluoride etherate, 116 Diisopinocampheylborane, 117, 182 Diisopinocampheylmethoxyborane, 86 Dimesitylmethylborane, 8 Dimethoxy[l-trimethylsilyl-l,2-buta-dienyl]borane, 218 (R,R)- and (S,S)-frans-2,5-Dimethyl-borolanes, 119... 

SYNTHESIS A solution of 5.50 g 2,5-dimethoxy-4-ethylthio-B-nitrostyrene (see under 2C-T-2 for its preparation) was made in 80 mL boiling anhydrous THF. On cooling, there was some separation of a fine crystalline phase, which was kept dispersed by continuous stirring. Under an inert atmosphere there was added 3.5 mL of a 10 M borane dimethylsulfide complex, followed by 0.5 g sodium borohydride as a solid. There was a slight exothermic response, and the color slowly faded. Stirring was continued for a week. There was then added 40 mL H,0 and 20 mL... 

SYNTHESIS A well-stirred solution of 1.77 g 2,5-dimethoxy-B-nitro-4-(n-propylthio)styrene (see under 2C-T-7 for its preparation) in 20 mL anhydrous THF was placed in an He atmosphere and treated with 1.5 mL of 10 M borane-dimethyl sulfide complex. This was followed by the addition of 0.2 g sodium borohydride, and the stirring was continued at room temperature for a week. The volatiles were removed under vacuum, and the residue was treated with 20 mL dilute HC1 and... 

N-(4-Nitrophenethyl)-l,2,3,4-tetrahydro-6,7-dimethoxy-l-methylisoquinoline N-(4-Nitrophenylacetyl)-l, 2,3,4-tetrahydro-6,7-dimethoxy-l-methylisoquinoline (62.9 g, 0.17 m) was added portion-wise to 500 ml of 1 M borane in THF which was diluted with 500 ml THF and maintained under nitrogen. The mixture was stirred at ambient temperature for 1 hr then heated to reflux for 4 hr. The mixture was then cooled in an ice bath and treated carefully with 20% HCI (250 ml). The mixture was refluxed for 1 hr, cooled and then the solvents evaporated on an aspirator. Water (1 liter) was added and the solution basified to pH 11 with 50% NaOH, then extracted with CHCI3 (3 x 300 ml). 

Boran Dimethoxy-(2-ethoxy-2-methylthio-vinyl)- XIII/3a, 767... 

ARIADNE itself, reduced not with LAH or AH (which would give the primary amine), but rather with sodium borohydride and borane dimethylsulfide. The product, 1-(2,5-dimethoxy-4-methylphenyl)-N-hydroxy-2-aminobutane hydrochloride, was a white crystalline material. The TOM analogue got as far as the nitrostyrene. This was made from 2-methoxy-4-methyl-5-(methylthio)benzaldehyde (see under the 5-TOM recipe for its preparation) and nitropropane in acetic acid, and gave bright yellow crystals. The true pseudo-analogue is the 2,4,6-trimethoxy material based on TMA-6, which is the "real" pseudo-TMA-2. The nitrostyrene from 2,4,6-trimethoxybenzaldehyde and nitropropane crystallized from MeOH/CH3CN as fine yellow crystals, and this was reduced with AH in cold THF to 1-(2,4,6-trimethoxyphenyl)-2-aminobutane which was a bright, white powder. 

---