Alane preparation

The finding of retention of configuration for this reaction demonstrates that free-radical intermediates are not involved. Lithium organoaluminates LiAlR4 are dimerized to RR by treatment with Cu(OAc)2." Terminal vinylic alanes (prepared by 15-17) can be dimerized to 1,3-dienes with CuCl in Symmetrical 1,3-dienes... 

Reagents of choice for reduction of epoxides to alcohols are hydrides and complex hydrides. A general rule of regioselectivity is that the nucleophilic complex hydrides such as lithium aluminum hydride approach the oxide from the less hindered side [511, 653], thus giving more substituted alcohols. In contrast, hydrides of electrophilic nature such as alanes (prepared in situ from lithium aluminum hydride and aluminum halides) [653, 654, 655] or boranes, especially in the presence of boron trifluoride, open the ring in the opposite direction and give predominantly less substituted alcohols [656, 657,658]. As far as stereoselectivity is concerned, lithium aluminum hydride yields trans products [511] whereas electrophilic hydrides predominantly cis products... 

Many more examples exist for reduction of the carhonyl only. Over an osmium catalyst [763] or platinum catalyst activated by zinc acetate and ferrous chloride [782] cinnamaldehyde was hydrogenated to cinnamyl alcohol. The same product was obtained by gentle reduction with lithium aluminum hydride at —10° using the inverse technique [609], by reduction with alane (prepared in situ from lithium aluminum hydride and aluminum chloride)... 

Acetals of aldehydes are usually stable to lithium aluminum hydride but are reduced to ethers with alane prepared in situ from lithium aluminum hydride and aluminum chloride in ether. Butyraldehyde diethyl acetal gave 47% yield of butyl ethyl ether, and benzaldehyde dimethyl acetal and diethyl acetal afforded benzyl methyl ether and benzyl ethyl ether in 88% and 73% yields, respectively [792]. 

Lithium aluminum hydride reduces preferentially the carbonyl function (p. 98) but alanes prepared by reactions of aluminum hydride with two equivalents of isopropyl or /er/-butyl alcohol or of diisopropylamine reduce the conjugated double bonds with high regioselectivity in quantitative yields [871] (p. 121). 

Reactivity of vinyl alanes Preparation of vinyl silanes Reactions of vinyl silanes Ate complexes from vinyl silanes... 

We have already seen examples of cuprates being used in stereochemically controlled conjugate additions to cyclopentenones and similar results can be achieved with ate complexes of vinyl alanes prepared by hydroalumination of alkynes to give e.g. 179 R = hexyl and hence the anti-A-product43 182. 

Several new aspects of organoalane chemistry have been described this year. Orthoesters react with alanes, prepared from a variety of allyl and propargyl halides, to give the corresponding 0,y-unsaturated acetals (Scheme 45). Interestingly reactions involving acetals rather than ortho esters lead exclusively to the formation of allenic ethers (160). ... 

Another group of isoprene polymerization catalysts is based on alanes and TiCl. In place of alkyl aluminum, derivatives of AlH (alanes) are used and react with TiCl to produce an active catalyst for the polymerization of isoprene. These systems are unique because no organometaHic compound is involved in producing the active species from TiCl. The substituted alanes are generally complexed with donor molecules of the Lewis base type, and they are Hquids or soHds that are soluble in aromatic solvents. The performance of catalysts prepared from AlHCl20(C2H )2 with TiCl has been reported (101). 

Professors Derek Hull, Colin Humphreys and Alan Windle of my Department in Cambridge have successively provided ideal facilities that have enabled me to devote myself to the preparation of this book. My thanks go to them. 

Many novel cluster compounds have now been prepared in this way, including mixed metal clusters. Further routes involve the oxidative fusion of dicarbon metallacarborane anions to give dimetal tetracarbon clusters such as (103) and (104) O (jjg insertion of isonitriles into inetallaborane clusters to give monocarbon meiallacarboranes such as (105) and the reaction of small ii/t/o-carboranes with alane adducts such as Et3NAlH3 to give the commo species (106) ... 

The substantial contributions of Alan Nadin and Eddy Yue to the preparation of this chapter are gratefully acknowledged. 

Grafstein, D., and C. Vogel The Chemistry of Alane, VI. Preparation of an Aluminium Difluoramide from Trimethylamine-Alane and Difluor-amine. J. Amer. chem. Soc. 88, 1576 (1966). 

In the Asia-Pacific region, AItingia excelsa Noronha (Liquidambar altingiana Bl.), Alan-gia gracilipes Hemsl. (Amyris ambrosiaca L.f.), Liquidambar orientalis Mill, and Liquidambar formosana Hance are of medicinal value. The purified basalm obtained from the trunk of Liquidambar orientalis Mill, or prepared storax (British Pharmaceutical Codex, 1969) has been used similarly as Peru basalm in the form of an ointment to treat scabies and other skin diseases, and as an ingredient of Compound Benzoin Tincture. 

As already was observed for hypercoordinated adducts MX3(ER 3)2, no stibine and bismuthine adducts of low-valent alanes, gallanes or indanes have been prepared, to date. According to the lability of low-valent group 13 compounds toward disproportionation into M(III) and elemental M, stibines and bismuthines are expected to be too weak as Lewis bases, preventing them from the stabilization of such compounds. 

The most stable of the germanium hydrides, R GcI I4 (n = 0,1,2,3), are the tri-organogermanium hydrides, which are prepared by the reduction of the corresponding halides with lithium alanate, or with amalgamated zinc and hydrochloric acid5-7. 

Extension of this reaction to electrophiles other than aldehydes was unsuccessful [22, 23], However, propargylic boronates were found to react with allylic halides and various carbonyl compounds [23], The boronates were prepared by lithiation of a methyl-substituted alkyne with t-butyllithium followed by treatment with a trialkylborane. The propargylic boronate preferentially reacts with the electrophile at the y-position to yield propargylic products (Eq. 9.20). The methodology has also been applied to alanates with comparable results. 

Although both boronates and alanates react with allylic bromides, aldehydes and C02 to afford allenic products in satisfactory yield, the alanates are more efficient in additions to ketones (Table 9.14). Boronate reagents do not require a B-C alkyl migration for their preparation. Thus the starting acetylene possesses the structural elements of the product. Additionally, the issue of dummy ligands is irrelevant. 

I appreciate the assistance of the editors, an anonymous reviewer, and, especially, D. Brandt Velbel and William M. Murphy, for their comments and criticisms. Dr. Alan S. Pooley of the Yale Peabody Museum assisted in taking the scanning electron photomicrographs of Figure 3. Preparation of this review was supported by NSF grant BSR-8514328. 

Alternatively, bromo trienyne 66, prepared by the Wittig reaction of TMS-capped propargyl ylide with , -5-bromo-2,4-pentadienal, could be coupled with dienyl zinc reagent 67, as illustrated in equation 3657. Subsequent desilylation followed by treatment with trimethyl aluminum in the presence of catalytic Cp2ZrCl2 afforded the alane of tetraenyne 68 which, on exposure to chloroformate, gave essentially all- polyene ester 69. 

Alan G. MacDiarmid Institute, Jilin University, Changchun, 130012, China State Key Lab of Inorganic Synthesis Preparative Chemistry, Jilin University, Changchun, 130012, China... 

A further synthetic approach to carbon-metal double bonds is based on the acid-catalyzed abstraction of alkoxy groups from a-alkoxyalkyl complexes [436 -439] (Figure 3.11). These carbene complex precursors can be prepared from alk-oxycarbene complexes (Fischer-type carbene complexes) either by reduction with borohydrides or alanates [23,55,63,104,439-445] or by addition of organolithium compounds (nucleophilic addition to the carbene carbon atom) [391,446-452]. 

M. Mamatha, B. Bogdanoviq M. Felderhoff, A. Pommerin, W. Schmidt, F. Schiith, C. Weidenthaler, Mechanochemical preparation and investigation of properties of magnesium, calcium and hthium-magnesium alanates , J. Alloys Compd. 407 (2006) 78-86. 

A PEG-star supported triphenylphosphine analog (66) was synthesized and employed in Mitsunobu reactions. Four phenolethers were prepared within 3-18 h reaction time and 68-93% yield. Upon completion of the reactions, the formed polymer supported triphenylphosphine oxide was isolated by precipitation from diethyl ether in > 85% yield. The reagent could be recycled by means of alane reduction (73%). 

Addition of alane and borane to alkenes affords a host of alkylated alanes and boranes with various reducing properties (and sometimes bizarre names) diisobutylalane (Dibal-H ) [104], 9-borabicyclo[3.3.1]nonane (9-BBN) (prepared from borane and 1,5-cyclooctadiene) [705], mono- [106,107] and diiso-pinocampheylborane (B-di-3-pinanylborane) (both prepared from borane and optically active a-pinene) [108], isopinocampheyl-9-borabicyclo[3.3.1 Jnonane alias B-3-pinanyl-9-borabicyclo[3.3.1]nonane (3-pinanyl-9-BBN) (prepared from 9-borabicyclo [3.3.1]nonane and a-pinene) [709], NB-Enanthrane prepared from 9-borabicyclo[3.3.1]nonane and nopol benzyl ether) [770] and others. ... 

Lithium aluminum hydride and alanes are frequently used for the preparation of hydrides of other metals. Diethylmagnesium is converted to magnesium hydride [777], trialkylchlorosilanes are transformed to trialkylsilanes... 

The reagent of choice for the reduction of ketals to ethers is alone prepared in situ from lithium aluminum hydride and aluminum chloride in ether. At room temperature ethers are obtained in 61-92% yields [792, 934]. Cyclic ketals prepared from ketones and 1,2- or 1,3-diols afford on hydrogenolysis by alanes alkyl P- or y-hydroxyalkyl ethers in 83-92% yields [792]. 

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