Aluminum complexes synthesis

The different ratios of 52/53 produced by cycloadditions performed at atmospheric and high pressure, and the forma tion of the unusual trans adducts 53, have been explained by the facts that (i) Diels-Alder reactions under atmospheric pressure are thermodynamically controlled, and (ii) the anti-endo adducts 52 are converted into the short-lived syn-endo adducts 54 which tautomerize (via a dienol or its aluminum complexes) to 53. The formation of trans compounds 53 by induced post-cycloaddition isomerization makes the method more flexible and therefore more useful in organic synthesis. 

The CO2 activation reactions seen for aluminum porphyrins are also observed for In(Por)Me (Por = OEP, TPP), which will insert CO2 in the presence of pyridine and under irradiation by visible light to give the acetato complex In(Por)OC(0)Me. The indium acetato product has been characterized by X-ray crystallography, whereas in the aluminum complex it was observed only by spectroscopy. An alternative synthesis of the acetato complex is by treatment of ln(Por)Cl by alumina and water, followed by acetic acid. For the indium and... 

Another broad class of compounds are the bridged carbene complexes. These compounds contain two identical or two different metal centers with the carbene centers bonded to both of the metal atoms in a bridging relationship. However, these binuclear complexes generally do not show classical carbene reactivity and will therefore not be discussed further, except to mention briefly the special case of the titanium-aluminum complex (3) developed by Tebbe and Grubbs and their coworkers.101 This, and related complexes, has proven to be particularly useful in organic synthesis, although its principal importance is in reactions other than cyclopropanations. 

In 2011, Gross et al. (11JA12899) have reported the synthesis of an aluminum complex of tetraiodinated corrole 35 (Scheme 16) by treating Al(III)-corrole 34 with N-iodosuccinimide (NIS) in acetonitrile (ACN). It exhibited red fluorescence and possessed a long-lived triplet excited state. 

Scheme 16 Synthesis of aluminum complex of tetraiodinated corrole.

Vincens, V., Le Borgne, A. and Spassky, N., Oligomerization of Oxiranes with Aluminum Complexes as Initiators , in Catalysis in Polymer Synthesis, Washington, DC, 1992, ACS Symp. Ser. 496, pp. 205-214. 

Caution. The synthesis should he conducted in a hood because of the possible toxicity of the unusually volatile aluminum complex. 

Snider, Phillips, and Cordova very cleverly combined two consecutive ene reactions with a formaldehyde Diels-Alder cycloaddition to produce a dihydropyran that has previously been used in a total synthesis of pseudomonic acid (39).54 Thus, 1,5-diene 32 underwent dimethyla-luminum chloride-catalyzed ene reaction with formaldehyde to afford 33 (Scheme 4-XV) as a 8 1 mixture of trans cis isomers (80%). Isomers were not separated since the cis compound did not undergo the subsequent Diels-Alder reaction. Treatment of acetate 34 with ethylaluminum dichloride and formaldehyde in CH2CI2-CH3NO2 (25°C, 12 hr) gave a 37% yield of adduct 38. This transformation presumably involves initial ene reaction of 34 to give 35, which reacted with formaldehyde to produce complex 36. A quasi-intramolecular Diels-Alder cycloaddition then ensued that led to 37. Hydrolysis of aluminum complex 37 gave the desired pyran 38. 

Malonate and related activated methylene compounds have also been used as the nucleophile in conjugate addition/Michael reactions. Taylor and co-workers have developed a new methodology that utilizes (salen)aluminum complexes such as 43 as a catalyst to effect the enantioselective conjugate addition to a,p-unsaturated ketones by a variety of nucleophiles.25 For example, nitriles, nitroalkanes, hydrazoic acids, and azides have found utility in this reaction. Additionally, cyanoacetate (42) has been demonstrated to undergo a highly enantioselective conjugate addition to 41. The Krapcho decarboxylation is then necessary to produce cyanoketone 44, an intermediate in the synthesis of enantioenriched 2,4-cw-di substituted piperidine 45. 

Cyanations. Aluminum complexes with diarylphosphine oxide groups possev cyanation of aldehydes and imines- with in a manner analogous to the Reisser asymmetric Strecker synthesis is applic reactivity of Me SiCN than HCN in the p catalytic amount while supplying stoichica... 

Cyanadons. Aluminum complexes of BINOLs (1) that are armed at C-3 and C-3 with diarylphosphine oxide groups possess both Lewis acid and base centers. Asymmetric cyanation of aldehydes and mines with MeaSiCN, and of quinolines and isoquinolines in a manner analogous to the Reissert reaction is successful (ee 70-90%). The asymmetric Strecker synthesis is applicable to conjugated aldimines and the higher reactivity of Me SiCN than HCN in the presence of 10 mol% of PhOH enables its use in catalytic amount while supplying stoichiometric HCN as the cyanide source. 

Evans, D.A., Janey, J.M., Magomedov, N. and Tedrow, J.S. (2001) Chiral salen-aluminum complexes as catalysts for enantioselective aldol reactions of aldehydes and 5-alkoxyoxazoles an efficient approach to the asymmetric synthesis of syn and anti P-hydroxy-a-amino acid derivatives. Angewandte Chemie - International Edition, 40, 1884—1888. 

C, Pm = 0.80). In 2007, Nomura et al. reported the synthesis of Schiff base aluminum complex 4 [88] with flexible but bulky BuMe2Si substituents, which exhibited the highest isoselectivity in the ROP of rac-LA to form isotactic stereoblock PLA materials with a Pm value of 0.98 and a of 210°C. More recently, highly active yttrium phosphasalen initiators were reported for the stereocontrolled ROP of rac-lactide [89]. Changing the phosphasalen structure enables access to isoselectivities (Pm = 0.84) or hetero-selectivities (P, = 0.87) (Fig. 1). 

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