A New Synthesis of l-Hydroxypipecolic Acid

Abstract

A new synthetic approach toward l-hydroxypipecolic acid is described. This reaction sequence involves eight steps overall, starting from commercially available and inexpensive l-glyceraldehyde acetal. The strategy makes use of readily available reagents and can be used as a preparative synthesis of l-hydroxypipecolic acid. Most of the reaction steps proceed with moderate-to-good yields and do not require any unusual or expensive reagents.

Synthesis and site selective C–H functionalization of imidazo-[1,2-a]pyridines

“…136 In 2020, the Jin group developed a photocatalyst-mediated alkylation of imidazo[1,2-a]pyridines regioselectively at the C5 position with alkyl N-hydroxyphthalimide (NHP) 239, with eosin Y as a photocatalyst, and trifluoromethanesulfonic acid as an additive, in dimethyl sulfoxide under a nitrogen atmosphere at rt for 48 h (Scheme 72). 137 A successful methylation at the C5 position of imidazopyridines was also achieved by the Yan group by the reaction of imidazopyridine with dicumyl peroxide (dcp) in acetic acid in a sealed tube under N 2 . The reaction scope was also increased with quinoxalin-2(1H)-ones and the desired methylation to 174 was achieved successfully with excellent yields.…”

Construction of N‐Heterocycles through Cyclization of Tertiary Amines

“…[23] Wang and co-workers developed ac yclization reaction between iodonium ylides 20 and simple tertiary amines 21 to generate ab road range of Nheterocycles 22 (Scheme 7). [24,25] This reaction is unique as the cyclization of unmodified tertiarya mines can proceed without the assistance of any transition-metal catalysta nd in the absence of an additional oxidant/hydrogen acceptor.I odonium ylides exhibited exceptional reactivity as they can form ah alogen-bonding complex with at ertiary amine to induce aS ET process. The in situ formed radical ion pair M16 undergoes a HATp rocess, resultingi nc leavage of aC (sp 3 )ÀHb ond to generate radical ion pair M17 and 20 b.S ubsequently, radical anion addition of iminium generates ar adicali ntermediate M18.U pon losing one molecule of iodobenzene, ani ntramolecular malonyl radical addition of the aromatic ring gives Nheterocycles 22.…”