Diels-Alder reaction, of acrolein with

The carbo-Diels-Alder reaction of acrolein with butadiene (Scheme 8.1) has been the standard reaction studied by theoretical calculations in order to investigate the influence of Lewis acids on the reaction course and several papers deal with this reaction. As an extension of an ab-initio study of the carbo-Diels-Alder reaction of butadiene with acrolein [5], Houk et al. investigated the transition-state structures and the origins of selectivity of Lewis acid-catalyzed carbo-Diels-Alder reactions [6]. Four different transition-state structures were considered (Fig. 8.4). Acrolein can add either endo (N) or exo (X), in either s-cis (C) or s-trans (T), and the Lewis acid coordinates to the carbonyl in the molecular plane, either syn or anti to the alkene. 

Fig. 8.4 The four different transition-state structures considered for the Diels-Alder reaction of acrolein with a diene in the presence of a Lewis acid (BH3). The diene can add...

A series of investigation using, e.g., semi-empirical calculations have also been performed [24]. These calculations are often used in relation with experimental investigations, as well as, e.g., the carbo-Diels-Alder reaction of acrolein with dienes. 

Diels-Alder reaction, of acrolein with B-butyl cyclohexenyl ether, n-butyl vinyl ether, and ethyl isopropenyl ether, 34, 30... 

Dicyclopen tadiene, 32,41 36,33 37,65 Dicyclopropyl ketone, 38,19 Diels acid, 35, 38 Diels-Alder reaction, of acrolein with n-butyl cyclohexenyl ether, n-butyl vinyl ether, and ethyl iso-propenyl ether, 34, 30 of butadiene with maleic anhydride, 30, 93... 

Supported Lewis acids are an interesting class of catalysts because of their operational simplicity, filterability and reusability. The polymer-bound iron Lewis-acid 53 (Figure 3.8) has been found [52] to be active in the cycloadditions of a, S-unsaturated aldehydes with several dienes. It has been prepared from (ri -vinylcyclopentadienyl)dicarbonylmethyliron which was copolymerized with divinylbenzene and then treated with trimethylsilyltriflate followed by THF. Some results of the Diels-Alder reactions of acrolein and crotonaldehyde with isoprene (2) and 2,3-dimethylbutadiene (4) are summarized in Equation 3.13. 

The chiral catalyst 142 achieves selectivities through a double effect of intramolecular hydrogen binding interaction and attractive tt-tt donor-acceptor interactions in the transition state by a hydroxy aromatic group [88]. The exceptional results of some Diels-Alder reactions of cyclopentadiene with substituted acroleins catalyzed by (R)-142 are reported in Table 4.21. High enantio- and exo selectivity were always obtained. The coordination of a proton to the 2-hydroxyphenyl group with an oxygen of the adjacent B-0 bond in the nonhelical transition state should play an important role both in the exo-endo approach and in the si-re face differentiation of dienophile. 

Indium trichloride [30] and methylrhenium trioxide [31] catalyze the aqueous Diels-Alder reaction of acrolein and acrylates with cyclic and open-chain dienes. Some examples of the cycloaddition of methyl vinyl ketone with 1,3-cyclohexadiene are reported in Scheme 6.18. MeReOs does not give satisfactory yields for acroleins and methyl vinyl ketones with substituents at the jS-position and favors the self-Diels-Alder reaction of diene. 

Density functional theory has been used to investigate the Diels-Alder reactions of triazolinedione with s-cis- and. y-fran -butadiene. " Combined quantum mechanics-molecular mechanics calculations have been used to investigate the asymmetric Diels-Alder reaction of cyclopentadiene with the complex dienophiles AICI3-methyl acrylate and methoxyaluminium dichloride-acrolein.Equilibrium constants have been determined for the molecular complexes formed from 1-alkyl-1-(2-naphthyl)ethenes and 1-vinylnaphthalene with TCNE in C1(CH2)2C1 at 27.1 °C ... 

A simple, commercially available chiral alcohol, a,a,a a -tetraaryl-l,3-dioxo-lane-4,5-dimethanol (TADDOL, 7a), catalyzes the hetero- and carbo-Diels-Alder reactions of aminosiloxydienes with aldehydes and a-substituted acroleins to afford the dihydropyrones and cyclohexenones, respectively, in good yields and high enan-tioselectivities. More recently, it was reported that axially chiral biaryl diols 7b and 7c were more highly effective catalysts for enantioselective hetero-Diels-Alder reactions (Scheme 12.5). ... 

Enantioselective Diels-Alder reactions of acrolein are also catalyzed by 3-(2-hydroxy-3-phenyl) derivatives of BINOL in the presence of an aromatic boronic acid. The optimum boronic acid is 3,5-di(trifluoromethyl)benzeneboronic acid, with which >95% e.e. can be achieved. The transition state is believed to involve Lewis acid complexation of the boronic acid at the carbonyl oxygen and hydrogen bonding with the hydroxyl substituent. In this transition state, re,re-interactions between the dienophile and the hydroxybiphenyl substituted can also help to align the dienophile.65... 

Predict the regioselectivity in the Diels-Alder reactions of acrolein and N-acetyl-2-cyano-4-phenyl-l-azabutadiene with 1-hexene, styrene, ethyl vinyl ether and methyl acrylate. The FOs of the azadiene are given below the others may be found in the Appendix. 

The second major route to tricyclic /3-lactams with a bridgehead nitrogen atom and extra heteroatom(s) is through cycloaddition reactions. Again, these may be of the intermolecular or intramolecular type. Diels-Alder reaction of acrolein and the cephems 420 gave 421 as the major products (Equation 65) <1996TL5967>. 

Table 2 Experimental and theoretical 2H and 13C KIEs for the Lewis acid catalyzed Diels-Alder reaction of isoprene with acrolein, methyl vinyl ketone and ethyl acrylate in toluene at 25°C...

Diels-Alder catalyst. The Diels-Alder reaction of cyclopentadiene with acrolein (equation I) catalyzed by BF3 etherate gives a mixture of endo- and exoadducts in the ratio 9 1. The endo-selectivity is improved by use of trimethylalu-minum. Introduction of a more bulky group on aluminum by use of DAD results... 

The moderate Lewis acidity of ruthenium complexes was used to promote catalytic Diels-Alder reaction of dienes and acrolein derivatives [21-23]. The enantioselective Diels-Alder reaction of methacrolein with dienes was catalyzed with cationic ruthenium complexes containing an arene or cyclo-pentadienyl (Cp) ligand and a chiral ligand such as phosphinooxazoline, pyridyl-oxazoline, monoxidized 2,2 -bis(diphenylphosphino)-1, T-binaphthyl (BINPO)or l,2-bis[bis(pentafluorophenyl)phosphanyloxy]-l,2-diphenylethane (BIPHOP-F). The reaction gave the cycloadduct in high yields with excellent... 

Bimey, D. M. Houk, K. N. Transition structures of the Lewis acid-catalyzed Diels-Alder reaction of butadiene with acrolein. The origins of selectivity, 7. Am. Chem. Soc. 1990,112, 4127-4133. 

Another hint toward understanding reaction dynamics on a bifurcating surface was supplied by Singleton in his study of the Diels-Alder cycloaddition of acrolein with methyl vinyl ketone (Reaction 8.12). Recognizing the interconversion of 87 and 88 through a Cope rearrangement along with careful kinetic analysis led to an estimate of the ratio of the rate of formation of 87 88 as 2.5 1. 

A typical Diels-Alder reaction of acrolein and cyclohexadiene was conducted by Zhang and coworkers using either fluorous imidazolidinone 63 or its standard counterpart 64 as the catalyst (Scheme 5.18) [78]. The product yield (86%), endo j exo ratio (93.4 6.6) and enantioselectivity (93.4% ee for the endo isomer) afforded by 63 were comparable to those of the control experiment with 64. The fluorous catalyst was examined in Diels-Alder reactions of other dienes and a,P-unsaturated aldehydes, providing consistently high enantioselectivities. In addition, 63 could be readily separated from the reaction products by F-SPE and recovered in 80-84% yields with excellent purity. 

The hetero Diels-Alder reaction of dihydropyran with acrolein (Scheme 2) was performed at 0 °C without solvent in the presence of H-form zeolites [11]. The best catalysts were dealuminated HY (Si/Al = 15 62% yield of the desired adduct) and H-beta (Si/Al = 25 65 % yield). The thermal reaction at 150 °C gave the adduct in 5 % yield only. 

Scheme 2. The Diels-Alder reaction of dihydropyran with acrolein catalyzed by H-form zeolites.

The Diels-Alder cycloaddition of acrolein with the (ft)-diene reported in reaction A affords a 4.5 1 ratio of the indicated diastereoisomers. When an enantiomerically pure (R)-dienophile is reacted with an achiral equivalent of the previous diene (Fig. 6 reaction B), two diastereoisomers are obtained in a 8 1 ratio. As the two major isomers of reactions A and B have the same configuration at the newly formed stereocenters, it can be anticipated that when the two enantiomerically pure (R)-partners are combined, the intrinsic stereoselection of each reactant is exalted to give a very stereoselective process. 

Diels-Alder reactions of cyclopentadiene with different alkenes proceed at different rates. Cyclopentadiene reacts with acrolein in ether at room temperature (24 h) to give a 95% yield of 27.59 contrasts with the reaction of cyclopentadiene and ethene in ether to give a 74% yield of norbornene (28), but required heating to 200°C in an autoclave at 5800 psi pressure or 32 h. The presence of an electron releasing group on the alkene causes the reaction to proceed with greater difficulty. Vinyl acetate reacted with cyclopentadiene at 190°C in an autoclave (10 h, neat) to give only 25% of 29. 

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