Boranes sec.

The following sections contain discussion of the boranes (Sec. 10-7), related substances (Sec. 10-8), ferrocene and related substances (Sec. 10-9), and other electron-deficient compounds (Sec. 10-10). 

Di(isopinocampheyl)borane Sec. alcohols from ketones Asym. reduction... 

Dimethylamine borane Sec. amines from azomethines Selective reduction... 

The yield of 17 is 50 62% in the reactions involving butyl- or. vw-butyllithium due to competitive transfer of the butyl or sec-butyl group. Yields of 17 are improved by using pyridine as the additive, but diastereoselectivity is not as high as when the alkyllithiums are employed. Without any additive, a complex mixture of syn- and anti-diastereomers plus products resulting from addition of the a-carbon of the substrate borane to the aldehyde are obtained. 

Sayles (Ref 67) combined n-butylferrocene with l-(2,3-epoxyaliphatic) carboianes of at least 3 carbonations in the aliphatic chain to function both as burning rate catalysts and cross-linking agents for carboxylated polybutadiene and acrylate binders. The use of 1,2-bis(2,3-epoxy-piopyl) carborane and 1-(2,3-epoxypropyl) car-borane boosted the burning rate of a butyl-ferrocene propint from 1.2 to 1.9 inches/sec as the data in Table 32 indicates... 

The thermal isomerization of tert. -butyl-diisobutylborane to triisobutylborane and the stepwise isomerization of triisopropyl and tri-sec.-butyl boranes to the corresponding straight-chain isomers have been studied over a range of temperature, both neat and using either the end product trialkylborane or diglyme as solvent117 . In all cases the reactions were first order and showed no solvent effect. 

Prslparativ wegen der hohen optischen Ausbeuten besonders interessant ist die von Brown und Zweifel (51, 53, 54, 325) entdeckte asymmetrische Hydroborierung 1,2-di- oder trisubstituierter Athylen-Doppelbindungen. Man setzt hierbei das aus (+)-a-Pinen, NaBH und BFg leicht zugang-liche (—)-Diisopinocamphenylboran VII mit cis-Olefinen um und oxy-diert die entstehenden Borane unter Retention der Konfiguration zu sec. Alkoholen. Auf diese Weise erhalt man z.B. aus cis-Buten-(2) mit p = 87% (R)(-)-Butanol- 2). 

For a discussion, sec Brown Boranes in Organic Chemistry, Cornell University Press Ithaca. NY. 1972, pp. 114-121. 

J,lFor reviews, see Pelter Smith Brown. Ref. 293, pp. 244-249 Brown Boranes in Organic Chemistry Cornell University Press Ithaca. NY, 1972, pp. 321-325 Mattcson in Hartley Patai, Ref. 1, vol. 4, pp. 307-409, pp. 337-340. Sec also Brown Snyder Subba Rao Zwcifcl Tetrahedron 1986, 42. 5505. 

For discussions of selectivity with metal hydride reducing agents, sec Brown Krishnamurthy Tetrahedron, 1979, 35. 567-607 Walker Chem. Soc. Rev. 1976,5, 23-50 Brown Boranes in Organic Chemistry, Cornell University Press Ithaca. NY, 1972, pp. 209-251, Rerick, in Augustine, Ref. 486. For books, sec, in Ref. 10, the works by Seydcn-Pcnnc, Strouf ct al. and Hajds. 

Scc Brown Heim Yoon J. Am. Chem. Soc. 1970,92. 1637 Cragg Orgnnoboranes in Organic Synthesis Marcel Dckkcr New York, 1973, pp. 319-371. For reviews of reductions with BH,. sec Wade J. Mol. Catal. 1983, IS, 273-297 (BH, and a catalyst) Lane Chem. Rev. 1976.76.773-799. Aldrichimica Acta 1977,10.41-51 Brown Krishnamurthy Aldrichimica Ada 1979, 12. 3-11. For reviews of reduction with boranc derivatives, sec Peltcr Smith Brown Borane Reagents-, Academic Press New York. 1988. pp. 125-164 Peltcr Chem. Ind. (London) 1976, 888-896. 

The principal innovations that have been made in the discussion of the theory of the chemical bond in this edition are the wide application of the electroneutrality principle and the use of an empirical equation (Sec. 7-10) for the evaluation of the bond numbers of fractional bonds from the observed bond lengths. A new theory of the structure of electron-deficient substances, the resonating-valence-bond theory, is described and used in the discussion of the boranes, ferrocene, and other substances. A detailed discussion of the valence-bond theory of the electronic structure of metals and intermetallic compounds is also presented. 

REDUCTION, REAGENTS Aluminum amalgam. Borane-Dimethyl sulfide. Borane-Tetrahydrofurane. t-Butylaminoborane. /-Butyl-9-borabicyclo[3.3.1]nonane. Cobalt boride— f-Butylamineborane. Diisobutylaluminum hydride. Diisopropylamine-Borane. Diphenylamine-Borane. Diphenyltin dihydride. NB-Enantrane. NB-Enantride. Erbium chloride. Hydrazine, lodotrimethylsilane. Lithium-Ammonia. Lithium aluminum hydride. Lithium borohydride. Lithium bronze. Lithium n-butylborohydride. Lithium 9,9-di-n-butyl-9-borabicyclo[3.3.11nonate. Lithium diisobutyl-f-butylaluminum hydride. Lithium tris[(3-ethyl-3pentylK>xy)aluminum hydride. Nickel-Graphite. Potassium tri-sec-butylborohydride. Samarium(II) iodide. Sodium-Ammonia. Sodium bis(2-mcthoxyethoxy)aluminum hydride. 

Trimethylamine-borane of good purity is commercially available or may be prepared on a large scale from NaBH4.8i (See Sec. 19C.) It may be easily purified by vacuum sublimation. Solvents may be dried over calcium hydride or molecular sieves. Caution. All syntheses should he carried out in a... 

Commercially available solutions of H3B-THF in THF (Aldrich-Boranes, Inc., 2371 N. 30th St., Milwaukee, WI 53210) which are used in this synthesis, contain approximately 5% of sodium tetrahydroboratefl —) as a stabilizer. Tri(sec-butyl)borane prepared from these solutions should be distilled. An alternative commercial (Aldrich-Boranes, Inc.) hydroborating agent free of sodium tetrahydroborate(l —) is borane-methyl sulfide. 

Boron is determined by oxidation of tri(sec-butyl)borane to 2-butanol.911,12 A 4.0-mL aliquot of the potassium tri(sec-butyl)hydro-borate(l — ) solution is hydrolyzed by adding it, with stirring, to a mixture of... 

Sec also the borane and carborane-manganese carbonyl compounds R. N. Grimes, in Comprehensive Organometallic Chemistry, ed, G. Wilkinson, F. G. A. Stone and E. W, Abel, Pergamon, Oxford, 1982, vol. 1, p. 459. 

Tetramethylethylenediamine, THE, sec-butyllithium, chlorodimethyloctylsilane THE, borane-tetrahydrofuran complex, hydrochloric acid CH2C12, vinyl chloroformate THE, potassium t-butoxide... 

NaCl (solid) The coordination number of each atom in the NaCl lattice is six. Therefore, further weakening of the Na-Cl bond is observed (c.f. Sec. 4.2.2.4). An instructive example illustrating the difference between terminal and bridging bonds is found among the boranes ... 

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