Diels-Alder reaction diethylaluminum chloride

Alkenylmethyl) cyclic ethers are formed by the reaction of lactols and alkenes." Diels-Alder reactions. Diethylaluminum chloride deposited on silica seems to be a superior catalyst. Methylaluminum dichloride alone is effective in promoting intramolecular cycloadditions involving a furan ring as the diene. ... 

Lewis acids such as zinc chloride, boron trifluoride, tin tetrachloride, aluminum chloride, methylaluminum dichloride, and diethylaluminum chloride catalyze Diels-Alder reactions.22 The catalytic effect is the result of coordination of the Lewis acid with the dienophile. The complexed dienophile is more electrophilic and more reactive toward electron-rich dienes. The mechanism of the addition is believed to be concerted and enhanced regio- and stereoselectivity is often observed.23... 

In 1990, Choudary [139] reported that titanium-pillared montmorillonites modified with tartrates are very selective solid catalysts for the Sharpless epoxidation, as well as for the oxidation of aromatic sulfides [140], Unfortunately, this research has not been reproduced by other authors. Therefore, a more classical strategy to modify different metal oxides with histidine was used by Moriguchi et al. [141], The catalyst showed a modest e.s. for the solvolysis of activated amino acid esters. Starting from these discoveries, Morihara et al. [142] created in 1993 the so-called molecular footprints on the surface of an Al-doped silica gel using an amino acid derivative as chiral template molecule. After removal of the template, the catalyst showed low but significant e.s. for the hydrolysis of a structurally related anhydride. On the same fines, Cativiela and coworkers [143] treated silica or alumina with diethylaluminum chloride and menthol. The resulting modified material catalyzed Diels-Alder reaction between cyclopentadiene and methacrolein with modest e.s. (30% e.e.). As mentioned in the Introduction, all these catalysts are not yet practically important but rather they demonstrate that amorphous metal oxides can be modified successfully. 

The Lewis acid catalyzed reaction of furan (169) with ketovinylphosphonate 170 produced a mixture of adducts, both of which slowly underwent retro Diels-Alder reactions at room temperature121. When diethylaluminum chloride was used as the catalyst, the endo selectivity (with respect to the keto functionality) was enhanced from 171/172 = 58/42 to 78/22 by raising the reaction temperature from — 25 °C to 0°C (equation 47). This is in agreement with the FMO theory, since initial Lewis acid complexation is with the phosphonate group. 

Sudo and Saigo153 reported the application of ds-2-amino-3,3-dimethyl-l-indanol derived l,3-oxazolidin-2-one 231 as a chiral auxiliary in asymmetric Diels-Alder reactions. The TV-crotonyl and TV-acryloyl derivatives were reacted with cyclopentadiene, 1,3-cyclohexadiene, isoprene and 2,3-dimethyl-l,3-butadiene, using diethylaluminum chloride as the Lewis acid catalyst. The reactions afforded the expected cycloadducts in moderate to high yields (33-97%) with high endo selectivities and high de values (92% to >98%). 

Kunieda and colleagues155 used a similar kind of l,3-oxazolidin-2-one (234) and studied the diethylaluminum chloride and boron trifluoride etherate catalyzed Diels-Alder reactions of its A-acryloyl and A-crotonyl derivatives with cyclopentadiene. The yields were high (80-100%), the reactions being almost completely endo selective. The diastere-omeric excesses obtained ranged from 71% to more than 99%. 

Carbohydrates have found widespread use as chiral auxiliaries in asymmetric Diels-Al-der reactions156. A recent example is a study conducted by Ferreira and colleagues157 who used carbohydrate based chiral auxiliaries in the Lewis acid catalyzed Diels-Alder reactions of their acrylate esters 235 with cyclopentadiene (equation 66). Some representative results of their findings, including the ratios of products 236 and 237, have been summarized in Table 9. The formation of 236 as the main product when diethylaluminum chloride was used in dichloromethane (entry 3) was considered to be the result of an equilibrium between a bidentate and monodentate catalyst-dienophile complex. The bidentate complex would, upon attack by the diene, lead to 236, whereas the monodentate complex would afford 236 and 237 in approximately equal amounts. The reversal of selectivity on changing the solvent from dichloromethane to toluene (entry 2 vs 3) remained unexplained by the authors. 

Cadogan and coworkers160 developed a fructose-derived l,3-oxazin-2-one chiral auxiliary which they applied in the Diels-Alder reactions of its iV-enoyl derivatives 246 with cyclopentadiene using diethylaluminum chloride as the Lewis acid catalyst. The reactions afforded mixtures of endo 247 and exo 248 (equation 68). The catalyst binds to the chiral dienophile in a bidentate fashion (co-ordination to both carbonyl groups). As a consequence, the dienophile is constrained to a rigid conformation which accounts for the almost complete diastereofacial selectivities observed. 

Taguchi and coworkers175 studied the Lewis acid catalyzed asymmetric Diels-Alder reactions of chiral 2-fluoroacrylic acid derivatives with isoprene and cyclopentadiene. When a chiral l,3-oxazolidin-2-one and diethylaluminum chloride were used as the chiral auxiliary and the Lewis acid catalyst, respectively, a de of 90% was observed for the reaction with isoprene. The reaction with cyclopentadiene afforded a 1 1 mixture of endo and exo isomers with de values of 95% and 96%, respectively. The endo/exo selectivity was improved by using 8-phenylmenthol as the chiral auxiliary. Thus, the reaction... 

Intramolecular Diels-Alder reactions resulting in bridgehead alkenes usually require high reaction temperatures. Consequently catalysts that permit use of lower temperatures are useful. Of a number of Lewis acids studied, diethylaluminum chloride was found to be the most efficient for the intramolecular cycloaddition of the triene 7 to 8 at 21°. The... 

Asymmetric Diels-Alder reactions. Chiral a,p-unsaturated N-acyl oxazolidones exhibit high diastereoface selection in Diels-Alder reactions, particularly those conducted in the presence of diethylaluminum chloride (1.2 equiv.). 

Diphenyl-BINOL-derived chiral aluminum reagents are prepared in situ by addition of Ethylaluminum Dichloride or Diethylaluminum Chloride to 3,3 -diphenyl-BINOL. These chiral aluminum reagents promote the enantioselective Diels-Alder reaction of cyclopentadiene with the oxazolidone dienophile (eq 14). Endo products are obtained with a high level of asymmetric induction (>90% ee) however, a stoichiometric amount of the Lewis acid is required. The preparation and use of a C3 symmetric BINOL-derived boronate has been reported (eq 15). BINOL-B(OAr)3 complexes have recently been developed for the asymmetric Diels-Alder reaction with imines (eq 16). ... 

A Lewis acid-mediated two-fold asymmetric Michael addition allows access to c( s-decalin derivatives. The reaction of the trimethylsilylenol ether of acety Icyclohexene with phenylmenthyl acrylate in the presence of Diethylaluminum Chloride (eq 7) yields the decalone in 64% yield (70% de). This has been shown not to be a Diels-Alder reaction. If the reaction is worked-up early, the initial Michael adduct can be isolated. ... 

Homo-Diels-Alder reactions occur between norbornadiene and norbornene or unactivated alkynes giving 14 and 15a-e , respectively, by using as catalyst the cobalt complex obtained by reducing tris(acetylacetonato)cobalt with diethylaluminum chloride in the presence of bis(l, 2-diphenylphosphino)ethane." ... 

The use of transition metal complexes as catalysts allows 1,4-cycloadditions to be involved as the major pathway in several cases when conjugated dienes are reacted with norbornadiene. No normal homo-Diels-Alder reaction was observed by reaction of the latter with buta-1,3-diene in the presence of an iron complex catalyst, the main product obtained was such a 1,4-adduct 2f the same adduct 2 was obtained in good yield and selectivity when a catalyst formed from cobalt(II) chloride, diethylaluminum chloride and bis(l,2-diphenylphos-phinojethane was used. ... 

Lewis acids such as zinc chloride, aluminum chloride, and diethylaluminum chloride catalyze Diels-Alder reactions. The catalytic effect is the result of coordination of the Lewis acid with the dienophile. 

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