3-Nitroacrylate, Diels-Alder reactions with

Recently, enhanced endo selectivity has been reported in the Diels-Alder reaction of fE -l-acetoxybuta-l,3-dienes with methyl fi-nitroacrylate The selectivity is compared with that of the reaction using l-methoxybuta-l,3-dienes and 1-trimethylsilyloxybuta-1,3-di-enes The degree of electron richness of a diene is an important consideration in endo eKO selectivity issues In particular, electron-rich dienes favor the formation of fixc-nitrocycload-ducts fEq 8 9 ... 

Functionalized nitroalkenes are important dienophiles in the Diels-Alder reaction. For example, ( )-methyl P-nitroacrylate is an important reagent in organic synthesis. The nitro group can be readily eliminated the Diels-Alder reaction of P-nitroacrylate is equivalent to that of ethyl propiolate with an inverse regiochemistry (Eq. 8.4).11... 

Diels-Alder reactions have been conducted on solid phase, with either the dieno-phile or the diene linked to the support [156]. The reaction conditions and the regio-and stereoselectivities observed are similar to those in solution [58,157,158]. Illustrative examples of Diels-Alder reactions leading to support-bound cyclohexenes are listed in Table 5.10. Further examples include the cycloaddition of polystyrene-bound 2-sulfonyl-l,3-butadiene and V-phenylmaIcimidc [51], the high-pressure cycloaddition of 1,3-butadienes to resin-bound 1 -nitroacrylates [95], and the intramolecular Diels-Alder reaction of styrenes with acrylates [159]. 

Although commercially available, 1-trimethylsilyloxy-1,3-butadiene (1) can be easily prepared by silylation of crotonaldehyde. It has often been used as a reactive diene in Diels-Alder reactions. For example, reaction with dimethyl acetylenedicarboxylate (2) affords the cyclohexadiene diester (3) in 68% yield. This initial Diels-Alder adduct can be converted into two different aromatic products by the proper choice of conditions namely, thermal elimination affords the phthalate (4), while oxidation produces the phenol (5), hoth in good yield (eq 1). Reaction with methyl 3-nitroacrylate (6) followed hy hydrolysis of the initial adduct (7) and elimination of the -nitro group leads to the cyclohexadienol (8) (eq 2). Many other Diels-Alder reactions of this type have been carried out using (1), as shown in Table 1. In general, the endo adduct is favored, especially at lower temperatures. 

B3LYP/6-311G (PCM) calculations have shown that the 4 + 2-cycloaddition of cyclopentadiene and -/ -nitrostyrene in nitromethane solution proceeded in a stepwise mechanism. Sulfanyl-methylene-5(4//)-oxazolones and -sulfanyl-a-nitroacrylates have been used as dienophiles in the Diels-Alder reactions to synthesize norbornene/ane amino acid derivatives suitable for peptide synthesis. Organoammonium salts of chiral triamine catalyse the Diels-Alder reaction of a-(carbamoylthio)acroleins with acyclic 1,3-dienes to produce cyclohexenes with sulfur-containing chiral quaternary carbons.The helical-chiral hydrogen-donor... 

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