Control of diastereoselectivity in the cyclization of dipropenyl ketone to 2,6-dimethyl-1-heterocyclo-hexan-4-one

Synthesis of (±)-Cylindricines A, D, and E

“…The pH has been shown to affect the stereochemical ratio in the formation of 4-piperidinones by double Michael addition of ammonia to dienones. 11 As expected, 11 lowering the pH favored the undesired trans isomer 10 at the expense of the desired cis isomer 4. Reaction of 5 in MeOH containing 60 mg of NH 4 Cl per mL of concentrated NH 4 OH (1:13 NH 4 + /NH 3 ) provided 47% of 4, 34% of 10, and 5% of 12 while a similar reaction containing 1 g of NH 4 Cl per mL of concentrated NH 4 OH (1.3:1 NH 4 + /NH 3 ) afforded 20% of 4, 26% of 10, and 9% of 12.…”

“…Heating 5 in 3:1 MeOH/concentrated NH 4 OH in a sealed tube at 73 °C for 16 h gave 56% of 4 , 19% of 10 , and 6% of 12 . The pH has been shown to affect the stereochemical ratio in the formation of 4-piperidinones by double Michael addition of ammonia to dienones . As expected, lowering the pH favored the undesired trans isomer 10 at the expense of the desired cis isomer 4 .…”

Tandem Catalysis: The Sequential Mediation of Olefin Metathesis, Hydrogenation, and Hydrogen Transfer with Single-Component Ru Complexes

“…Complexes (PCy 3 ) 2 Cl 2 Ru=CHPh (1) 1 and (H 2 IMes)(PCy 3 )Cl 2 Ru=CHPh (2) 2 and substrates 1,6-heptadien-4-one (6), 3 1,8-nonadien-5-one (12), 4 2-allyl-2-(2-methyl-allyl)-malonic acid diethyl ester (15), 5 1,4-bis-allyloxy-but-2-yne (21), 4 2-methyl-acrylic acid but-3-enyl ester (24), 6 N-allyl-N-isopropyl-acrylamide (27), 7 and undec-10-enoic acid but-3-enyl ester (30) 8 were prepared as previously reported.…”

The endo-aza-Michael addition in the synthesis of piperidines and pyrrolidines

“…A later study from the same laboratory focused on the stereochemical outcome in the case of 2,6-disubstituted piperidine formation (Scheme 5). 6 Thus diallylketone 13 was treated with various primary amines to give, firstly isomerisation to the sensitive ketone 1, followed by the double aza-Michael addition. While the equilibrium ratio of the two products, cis-2 and trans-2, was claimed to be about 1:1, a more acidic medium, achieved by addition of ammonium salts, favoured formation of the cis isomer, while a more basic medium biased the ratio in favour of the trans isomer.…”