High-Pressure Promoted Cycloadditions of Enol Ethers and 3-Aryl-2-cyano-2-propenoates

Abstract

The high-pressure promoted cycloadditions of enol ethers (1) and alkyl 3-aryl-2-cyano-2-propenoates (2) lead stereoselectively in high yields to 2,6-dialkoxy-4-aryl-3,4-dihydro-2H-pyran-5-carbonitriles (3). These cycloadducts have a high potential for further synthesis due to the presence of various functionalities. This is illustrated with some representative conversions. As reactive cyclic ketene acetals the cycloadducts 3 were easily hydrolyzed to aldehydes (6) or ketones or alcoholized to acetals having additional ester and cyano

High Pressure‐Promoted [2+2] Cycloaddition Reactions of 4‐Methylphenyl 1,2‐Propadienyl Sulfone with Enol Ethers

“…Two diastereomers 7c and 7c′ were found in a ratio of 2:1. This is similar to the induction recently found when this enol ether was used in a [4+2] cycloaddition reaction with an enone system 11.…”

High Pressure‐Promoted [2+2] Cycloaddition Reactions of 4‐Methylphenyl 1,2‐Propadienyl Sulfone with Enol Ethers

“…Two diastereomers 7c and 7c′ were found in a ratio of 2:1. This is similar to the induction recently found when this enol ether was used in a [4+2] cycloaddition reaction with an enone system 11.…”

High-Pressure Hetero-Diels−Alder Route to (±)-6,6,6-Trifluoro-β-C-Naphthyl Glycosides

“…9b Scheeren and co-workers evidenced the synergistic effects of Eu(fod) 3 -catalysis and high pressure conditions in the formation of dihydropyrans from vinyl ethers. 17 Compressing heterodiene 6c with 7 to 13 kbar in the absence of any Lewis acid, however, was not sufficient to promote the in our case (Table 2, entry 5). In contrast, activation by Lewis acid and 13 kbar pressure at 50 °C showed the positive impact of the multiactivated process and allowed the formation of the cis-adducts 14 and 15, in a complete endo-selective manner (entries 6 and 7).…”

“…Interestingly, Schmidt’s group demonstrated the efficiency of hyperbaric conditions (6.2 kbar) on HDA reactions involving styrenes . Scheeren and co-workers evidenced the synergistic effects of Eu(fod) 3 -catalysis and high pressure conditions in the formation of dihydropyrans from vinyl ethers …”

High pressure in organic chemistry on the way to miniaturization

“…For instance, under high pressure conditions (15 kbar), 4-methylphenyl 1,2-propadienyl sulfones and enol ethers undergo a regioselective methylphenyl sulfones in good yields, while at atmospheric pressure the reaction does not take place. 134 Another interesting example reported by Aben et al 135 involves the reaction of enol ethers and alkyl 3-aryl-2-cyano-2-propenoates at high pressure to give the cycloadducts in high yields and stereoselectivities. The obtained products are attractive scaffolds for use in combinatorial chemistry, due to the presence of a sulfonyl group, a methylene function, and an alkoxy group, while the cyclobutane ring can either be left as a basic structural unit or can be involved in further conversions.…”

High Pressure‐Promoted [2+2] Cycloaddition Reactions of 4‐Methylphenyl 1,2‐Propadienyl Sulfone with Enol Ethers

“…Two diastereomers 7c and 7c′ were found in a ratio of 2:1. This is similar to the induction recently found when this enol ether was used in a [4+2] cycloaddition reaction with an enone system 11.…”

High-Pressure Hetero-Diels−Alder Route to (±)-6,6,6-Trifluoro-β-C-Naphthyl Glycosides

“…9b Scheeren and co-workers evidenced the synergistic effects of Eu(fod) 3 -catalysis and high pressure conditions in the formation of dihydropyrans from vinyl ethers. 17 Compressing heterodiene 6c with 7 to 13 kbar in the absence of any Lewis acid, however, was not sufficient to promote the in our case (Table 2, entry 5). In contrast, activation by Lewis acid and 13 kbar pressure at 50 °C showed the positive impact of the multiactivated process and allowed the formation of the cis-adducts 14 and 15, in a complete endo-selective manner (entries 6 and 7).…”

“…Interestingly, Schmidt’s group demonstrated the efficiency of hyperbaric conditions (6.2 kbar) on HDA reactions involving styrenes . Scheeren and co-workers evidenced the synergistic effects of Eu(fod) 3 -catalysis and high pressure conditions in the formation of dihydropyrans from vinyl ethers …”

High pressure in organic chemistry on the way to miniaturization

“…For instance, under high pressure conditions (15 kbar), 4-methylphenyl 1,2-propadienyl sulfones and enol ethers undergo a regioselective methylphenyl sulfones in good yields, while at atmospheric pressure the reaction does not take place. 134 Another interesting example reported by Aben et al 135 involves the reaction of enol ethers and alkyl 3-aryl-2-cyano-2-propenoates at high pressure to give the cycloadducts in high yields and stereoselectivities. The obtained products are attractive scaffolds for use in combinatorial chemistry, due to the presence of a sulfonyl group, a methylene function, and an alkoxy group, while the cyclobutane ring can either be left as a basic structural unit or can be involved in further conversions.…”

High Pressure‐Promoted [2+2] Cycloaddition Reactions of 4‐Methylphenyl 1,2‐Propadienyl Sulfone with Enol Ethers

“…Two diastereomers 7c and 7c′ were found in a ratio of 2:1. This is similar to the induction recently found when this enol ether was used in a [4+2] cycloaddition reaction with an enone system 11.…”

High-Pressure Hetero-Diels−Alder Route to (±)-6,6,6-Trifluoro-β-C-Naphthyl Glycosides

“…9b Scheeren and co-workers evidenced the synergistic effects of Eu(fod) 3 -catalysis and high pressure conditions in the formation of dihydropyrans from vinyl ethers. 17 Compressing heterodiene 6c with 7 to 13 kbar in the absence of any Lewis acid, however, was not sufficient to promote the in our case (Table 2, entry 5). In contrast, activation by Lewis acid and 13 kbar pressure at 50 °C showed the positive impact of the multiactivated process and allowed the formation of the cis-adducts 14 and 15, in a complete endo-selective manner (entries 6 and 7).…”

“…Interestingly, Schmidt’s group demonstrated the efficiency of hyperbaric conditions (6.2 kbar) on HDA reactions involving styrenes . Scheeren and co-workers evidenced the synergistic effects of Eu(fod) 3 -catalysis and high pressure conditions in the formation of dihydropyrans from vinyl ethers …”

High pressure in organic chemistry on the way to miniaturization

“…For instance, under high pressure conditions (15 kbar), 4-methylphenyl 1,2-propadienyl sulfones and enol ethers undergo a regioselective methylphenyl sulfones in good yields, while at atmospheric pressure the reaction does not take place. 134 Another interesting example reported by Aben et al 135 involves the reaction of enol ethers and alkyl 3-aryl-2-cyano-2-propenoates at high pressure to give the cycloadducts in high yields and stereoselectivities. The obtained products are attractive scaffolds for use in combinatorial chemistry, due to the presence of a sulfonyl group, a methylene function, and an alkoxy group, while the cyclobutane ring can either be left as a basic structural unit or can be involved in further conversions.…”