Cyclopentadiene with methyl acrylate

Pagni and coworkers [18] have conducted in-depth investigations on the cycloadditions of cyclopentadiene with methyl acrylate on alumina of varing activity (200 300 400 800 °) showing that the diastereoselectivity of the... 

The micellar effect on the endo/exo diastereoselectivity of the reaction has also been investigated. The endo/exo ratio of the reaction of cyclopentadiene with methyl acrylate is affected little (compared to water) by the use of SDS and CTAB [73b], while a large enhancement was observed in SDS solution when n-butyl acrylate was the dienophile used [74]. The ratio of endo/exo products in the reaction of 1 with 113c is not affected by CTAB, SDS and C12E7 [72a]. 

Chloroaluminate ionic liquids (typically a mixture of a quaternary ammonium salt with aluminum chloride see Table 6.9) exhibit at room temperature variable Lewis acidity and have been successfully used as solvent/catalyst for Diels-Alder reactions [57]. The composition of chloroaluminate ionic liquids can vary from basic ([FMIM]C1 or [BP]C1 in excess) to acidic (AICI3 in excess) and this fact can be used to affect the reactivity and selectivity of the reaction. The reaction of cyclopentadiene with methyl acrylate is an example (Scheme 6.31). 

The diastereoselectivity of the cycloaddition of cyclopentadiene with methyl acrylate in SC-CO2 at 40 °C and subcritical liquid CO2 at 22 °C is practically the same endojexo = 75 25 and 76 24 respectively) and is comparable to that found in hydrocarbon solvents (73 27 and 75 25 in heptane and cyclohexane, respectively). This shows that CO2, in these states, behaves like an apolar solvent with very low polarizability [82]. 

The Diels-Alder reaction of cyclopentadiene with methyl acrylate in methanol was studied by Berson et al. [72] under conventional conditions, and shown to give a mixture of the endo and exo isomers 48 and 49 (Scheme 4.26). 

The asymmetric Diels-Alder reaction of cyclopentadiene with methyl acrylate lib has been studied using several types of catalysts. The asymmetric induction of various... 

This explains the experimentally confirmed predictions that polar solvents attenuate the endo-preference, while non-polar solvents increase the cwdo-selectivity of Diels-Alder reactions. The strong correlation between the polarity of the solvent and the endo/exo ratios in the Diels-Alder reaction led to the empirical polarity scale 2 = log endo/exo) using the reaction of cyclopentadiene with methyl acrylate as the standard144. The importance of solvent polarity has also been discerned on the basis of experimental142 and theoretical investigations145. Dependence on the polarizability was also noted146. 

Some chiral 1,3,2-dioxastannolanes were used as catalysts in asymmetric Diels-Alder reactions of cyclopentadiene with methyl acrylate <90JCR(S)278>. A-Alkenyl- and -cycloalkenyl 1,3,2-oxaza-stannolanes, generated in situ from chiral amino alcohols, gave optically active 2-substituted aldehydes and ketones in modest to high chemical and optical yields after alkylation with methyl acrylate or acrylonitrile (which is usual for enamines) and subsequent hydrolysis <85CC504,85JOC3863>. 

With Chiral Al Complexes Chiral bis(silyl)binaphthol-modified aluminum catalyst, which is originally developed for asymmetric hetero-Diels-Alder reaction [50], is successfully applied to asymmetric Diels-Alder reaction of cyclopentadiene with methyl acrylate or methyl propio-late [51 ] (Eq. 8A.28). The latter is a rather rare example in the literatures. 

With Chiral DiolTTi Complexes Harada investigated the influence of the torsional angles of biaryl rings on the enantioselecdvity in the asymmetric Diels-Alder reaction of cyclopentadiene with methyl acrylate catalyzed by a series of Ti complexes possessing chiral 2,2 -biaryldiols. The best results were obtained by the use of chiral binaphthol or 6,6 -hexylenedioxy-2,2 -biphenyldiol [52] (Eq. 8A.29). 

Chiral alkyldihaloboranes are among the most powerful of chiral Lewis acids. The Diels-Alder reaction of cyclopentadiene with methyl acrylate proceeded smoothly at — 78 °C in the presence of 530 or 531 to give the endo-adduct with >99% ee (Equation (250)).1046-1052... 

Kamahori K,Tada S, Ito K, Itsuno S (1995) Tetrahedron Asymmetry 6 2547 Kamahori K, Ito K, Itsuno S (1996) J Org Chem 61 8321 Takasu M, Yamamoto H (1990) Synlett 194 Sartor D, Saffrich J, Helmchen G (1990) Synlett 197 Hawkins JM, Loren S (1991) J Am Chem Soc 113 7794 Hawkins JM, Loren S, Nambu M (1994) J Am Chem Soc 116 1657 A modified isopinocampheyldibromoborane catalyzes the reaction of cyclopentadiene with methyl acrylate in 48% ee Bir G, Kaufmann D (1990) J Organomet Chem 390 1 A Lewis acid derived from JY-tosyl tryptophan and l,8-naphthalenediylbis(dichlorobo-rane) is reported to catalyze the Diels-Adler reaction of methacrolein sind cyclopentadiene in 100% ee for the endo isomer (endo/exo = 37 63) ReiUy M, Oh T (1994) Tetrahedron Lett 35 7209... 

The Diels-Alder reaction has been shown to be subject to catalysis by a wide range of solid catalysts (see Chapter 4 for some examples). Acidic mesoporous aluminosilicates can be used to catalyse selective Diels-Alder reactions such as that between cyclopentadiene with methyl acrylate. The zinc-exchanged version of the material is particularly effective and compares well to other more established solid acids such as the ion-exchanged clay Zn2+-K10 as well as homogeneous catalysts such as boron trifluoride (Table 2.7).50... 

Diels-Alder reactions of cyclopentadiene with methyl acrylate [19], (-)-menthyl acrylate, or other chiral dienophiles [20-23] catalyzed by cation-exchanged KIO montmorillonites were thoroughly investigated by Mayoral and co-workers. The structures of the chiral dienophiles are depicted in Figure 1. Moderate diastereo-selectivities were obtained with (-)-menthyl acrylate (54 %) and (7 )-f -acryloyl-pantolactone (53 %) in reactions catalyzed by zinc(II)-exchanged KIO montmoril-lonite at —20 °C. 

The Diels-Alder reaction between cycloalkanones (155) and cyclic dienes (154) in toluene and catalyzed by AICI3 under the action of microwave irradiation was reported by Reddy [88]. Reactions were performed in a domestic microwave oven and gave adducts in good yields within 2 min (Scheme 5.44). Interestingly, it was also observed that microwave irradiation increased selectivity for the endo product. This result is in contrast with that reported by Gedye [89] in the cydoaddition of cyclopentadiene with methyl acrylate in methanol. In this reaction, significant modification of endo/ exo selectivity, in comparison with previously reported results, was not observed. 

The Alder rule is not perfect. It correctly predicts the major product from the Diels-Alder reaction of 1,3-cyclopentadiene with methyl acrylate, but is incorrect in the case of methyl methacrylate. On the basis of these facts, give the structure of the major product isolated in each case. 

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