Stereoselective synthesis of optically active 2-alkylpiperidines utilizing electrochemical oxidation as a key step

Synthesis and Reactivity of β-Methoxymethyl Enecarbamates

“…Despite the fact that endocyclic analogues of this conjugated iminium ion have proven synthetically useful, , the synthesis and reactivity of exocyclic α,β-unsaturated N -acyliminium ions remains relatively unexplored with the exception of a single publication by our group relating to cycloaddition chemistry…”

“…While α-alkoxycarbamates have been obtained from N -acyl lactams by hydride reduction, in the present work, a simple electrochemical method was adopted. Toward this end, the anodic α-oxidation of 4 , 7 , and 8 with the Ross−Eberson−Nyberg procedure afforded high yields of N , O -acetals 9 − 11 . The high-yielding conversion of 9 to 12 was next accomplished by NH 4 Cl mediated elimination .…”

Ring Contraction of α,β-Unsaturated Cyclic Amines with cis-Dihydroxylation at the α,β-Position

“…Starting from readily commercially available cyclic amines 4a-f, we activated the α-position by electrochemical oxidation in methanol 5 followed by acid catalyzed removal of methanol to afford α,β-unsaturated cyclic amines 1a-f. 6,7 These results are summarized in Table 1. 4a 4b 4c 4d 4e 4f 2 3 5 3 4 3 1a 1b 1c 1d 1e 1f 96 95 70 96 95 87 Having successfully prepared 1a-f, we embarked on the task of functionalizing and subsequent ring opening of the product 2a-f. First, dihydroxylation of 1a-f using OsO 4 followed by thermodynamically induced ring opening by use of elevated temperatures afforded 3a-f.…”

Update 1 of: C2-Symmetric Chiral Bis(oxazoline) Ligands in Asymmetric Catalysis

“…Enantiomeric excess (%) vs ring size of the cis-fused cyclopropanes for the intramolecular reaction of 62 and 65 (refs − ).…”

“…The mechanism of elimination/addition occurs through the cation 240 as intermediate. This undergoes the enantioselective addition of malonate to position 2 to give the 1-acyl-3,4-didehydro-2-piperidyl malonates 241 (Scheme ). − Depending on the reaction conditions and substituents, some side-products, derived from the attack at position 4 of 240 , are also formed. The yields are in the range 36–86%, and the enantioselectivities are in the 21–95% ee range.…”