Dialkyl aluminum

The alkyl methacrylate monomers were available from various sources. Isobutyl methacrylate (IBMA) (Rohm and Haas) and t-butyl methacrylate (TBMA) (Rohm Tech) may be purified first by distillation from CaH, followed by distillation from trialkyl aluminum reagents as described in detail earlier (20,21). In particular, t-butyl methacrylate (b.pt. 150°C) was successfully purified by distillation, from triethyl aluminum containing small amounts of diisobutyl aluminum hydride. The trialkyl aluminum and dialkyl aluminum hydride reagents were obtained from the Ethyl Corporation as 25 weight percent solutions in hexane. The initiator, -butyllithium, was obtained from the Lithco Division of FMC, and analyzed by the Gilman "double titration" (22). 

Chiral a,/ -unsaturated A-acyloxazolidinones have been regarded as a complement for type I dienophile reagents. Evans et al.4 reported a Diels-Alder reaction promoted by dialkyl aluminum chloride. In this reaction, chiral a,/ -unsaturated A-acyloxazolidinones were used as highly reactive and diaster-eoselective dienophiles. The stereogenic outcome of the Diels-Alder adducts... 

In this mechanism, the stereoregulation in the propagation reaction is realized faithfully by the steric effect acting between the incoming monomer and the growing end monomeric unit, both of which have interactions with an aluminum atom. The penta-coordinate aluminum atom of the catalyst, which is similar to that shown in the dimeric acetaldehyde-catalyst complex, plays an important role as an intermediate compound or as a transition state. In principle, an identical mechanism may be applied to the polymerization by the dialkyl-aluminum monoalkoxide catalyst. 

Ballard et al. [64] found that bulky dialkyl aluminum phenolate additives would improve the anionic polymerization of acrylic monomers. They called their method Screened Anionic Polymerization (Scheme 28). 

Because of the large excess of ethylene present in the growth reactor, the reverse reaction is insignificant. Ethylene reacts with dialkyl aluminum hydride much more rapidly than does the terminal olefin, and any alkyl group thermally displaced is replaced by an ethyl group. However, terminal olefin present in the growth reactor can react with trialkylaluminum compounds. The a-olefin inserts between the aluminum-carbon bond just as ethylene does in a normal growth process. 

C. Reduction of Isoquinoline with Lithium Aluminum Hydride or Dialkyl Aluminum Hydride... 

Isoquinolinium salts are reduced to 2-alkyl-1,2-dihydroisoquinoline derivatives by sodium dithionite,6 lithium aluminum hydride7,8 (LAH), or dialkyl aluminum hydrides.9 LAH is preferred7 to dithionite since it leads to purer products, and will reduce those salts that are inert to dithionite (e.g., papaverine methiodide). Isoquinoline itself10,11 and 3-methyl-6,7-methylenedioxyisoquinolinelz (5) can be reduced to the 1,2-dihydroisoquinoline with LAH, as can isoquinoline... 

In alkylations of metal halides with A1R3 usually only one alkyl group is transferred, since the dialkyl aluminum halides are much less powerful alkylating agents than the trialkyls. The alkylaluminums react with compounds having acidic hydrogen atoms to give the alkane in some cases alkylation may occur, for example,... 

Careful and extensive kinetic studies have been carried out only for hydroaluminations with dialkyl-aluminum hydrides. Adequate kinetic information is still lacking on transition metal catalyzed hydroalumination and on the hydroaluminating action of complex metal hydrides, MAlRnH4 n. Preliminary studies on the nickel-catalyzed process have revealed an unstable rate behavior brought about by the deactivation of the catalyst with time. ... 

The formal addition of an alkyl halide (RX) to the C=C double bond of the Michael acceptors proceeded in a one-pot process by initial 1,4-addition of the dialkyl aluminum chloride and subsequent trapping of the enolate intermediate with A -halosuccinimides [148]... 

X-ray examination showed these polymers to be highly crystalline with the polymer assuming a helical configuration (Fig. 2). A soluble catalyst consisting of a combination of dialkyl aluminum halide and vanadium tetrachloride gives a regular structure with alternating d and 1 placements (syndiotactic) (18). Certain other soluble catalysts or those based on non-crystalline... 

Stereocontrol at the / -position is also observed in the photochemical reaction of dialkyl aluminum chlorides with acryloxy derivatives of (4S)-phenylmethyl-2-oxazolidinone23. The detailed mechanism of the reaction is not known. 

The synthesis of trialkyl alanes may be performed in practice in two ways. Either the three components are allowed to react in the presence of preformed trialkyl alane (one-stage process), or one carries out the reaction in two separate stages. This is more advantageous in many cases. In the first stage 2 moles of trialkyl alane react with activated aluminum in the presence of hydrogen to give 3 moles of dialkyl aluminum hydride (dialkyl alane) ... 

Substituents in the alkyl chain of alkyl aluminum compounds, such as halogens, alkoxy, alkylmercapto, or dialkylamino groups, have varying effects on the stability of the aluminum alkyls to extents which depend on the position of the group in relation to the aluminum. Interaction between the substituents and aluminum leads to activation of both the A1—C and the C-substituent bonds. If, in the case of dialkyl halomethylalanes, the substituent (Cl, Br, or I) and the aluminum are linked to the same carbon atom, the compound is especially reactive. These compounds, since their etherates are stable, may be prepared readily in ethereal solution from dialkyl aluminum halides and diazomethane 97, 98) ... 

In the free state the compounds decompose at once into dialkyl aluminum halide and hydrocarbon (mainly ethylene with a little cyclopropane). But at very low temperatures ( —80°C) it is possible to isolate, for example, iodomethyldiethylalane in hydrocarbon (pentane) solution 97, 98). 

Dialkyl aluminum chlorides and dialkyl aluminum amides, R2AINR2, are dimeric (56, 103, 122) ... 

When dialkyl aluminum hydride, chloride, or alcoholate is mixed with trialkyl alanes, rapid alkyl exchange takes place. This indicates that in such mixtures mixed association products such as... 

Dialkyl aluminum hydrides and di- or monoalkyl aluminum halides (with the exception of dialkyl aluminum fluorides) also add the donors mentioned... 

B. Reactions of the A1—H Bond with Unsaturated Hydrocarbons 1. Dialkyl Aluminum Hydrides, RiA IH, and Alkenes... 

Addition of dialkyl aluminum hydrides (dialkyl alanes) to C=C double bonds in alkenes (hydroalumination) leads to trialkyl alanes (291, 298). For the preparation of higher trialkyl alanes it is proposed to add diethyl-alane to higher 1-alkenes and from the resulting ethyl-alkyl alane mixtures (analogous to the organoboron compounds) (142) to remove the ethyl groups as triethylalane by distillation (241) ... 

The breakdown of the A1—C bonds takes place at increased temperatures and gives the dialkyl aluminum hydride and alkene (dehydroalumination) (293). In the equilibrium... 

Dialkyl Aluminum Hydrides and Alkenes with Functional Groups... 

Dialkyl alanes may be added to a variety of substituted alkenes. Stable or unstable alkyl aluminum compounds are formed, depending upon the nature and location of the substituent in the alkene. An important part is also played by the direction of addition of the A]—H bond, which can be influenced by the substituents. Unstable alkyl alanes with functional groups mostly spontaneously go over as formed to alkenes and dialkyl aluminum compounds with the substituent directly bonded to the aluminum (e.g., R2AIX, R2A10R ) as a result of l,x elimination. 

Among the stable alkyl alanes with substituents in the alkyl group are the silylated compounds. In the compound formed from diisobutyl-alane and triethylvinylsilane, the dialkyl aluminum group is found to the extent of about 70% on the internal carbon atom (70) ... 

Allyl chloride or allyl bromide and dialkyl aluminum hydrides do not give halogenoalkyl alanes, the products being dialkyl aluminum monohalides and propene 270) ... 

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