High-yielding method for preparation of carbocyclic or N-containing heterocyclic β-keto esters using in situ activated sodium hydride in dimethyl sulphoxide

Abstract

It was found that NaH suspension in DMSO was highly activated when reacted with an alcohol. The in situ generated NaH/alkoxide mixture permitted very rapid and complete deprotonation and acylation of various cyclic ketones with alkyl carbonates at ambient temperature. Activated NaH/ alkoxide in DMSO is particularly effective in Dieckmann condensations, where it affords 5-and 6membered carbocyclic or N-containing heterocyclic β-keto esters in high yields. A heterocyclic Dieckmann condensation was performed on a molar scale, demonstrating the scalability of the procedure. Besides, DMSO is non-toxic, relatively inexpensive and environmentally benign solvent.

Synthetic route towards potential bivalent ligands possessing opioid and D2/D3 pharmacophores

“…While N-aryl piperazines are commercially available, the norfentanyl 4 was obtained according to a known literature procedure. [19][20][21][22] For the starting material in the first alkylation step, norfentanyl 4 was selected as it was more readily available than the N-aryl piperazine 2. However, it was expected that both secondary amines would react similarly in this reaction.…”

Octahydrocyclopenta[c]pyridine Scaffold – Enantioselective Synthesis and Indole Annulation

“…We started the investigation with the preparation of N ‐protected methyl 4‐piperidone‐3‐carboxylates 8a – 8c (Scheme ). The N ‐Boc and N ‐benzyl protected congeners 8a and 8c were literature known and were prepared accordingly. N ‐Trifluoroacetamide 8b was a new compound and was prepared in analogy to the known ethyl ester .…”

“…GLC analyses were performed on a GC‐2010 Plus (Shimadzu) on a Lipodex E capillary column (Macherey–Nagel, 30 m, 0.25 mm) with H 2 as carrier gas. Compounds 8a , 8c , and N ‐Boc‐( S )‐Npg were literature known and prepared according to published procedures. All other starting materials were commercially available.…”

Synthetic route towards 1,2,3,4-tetrahydroquinoxaline/piperidine combined tricyclic ring system

“…to our previously published procedure. 37 The N-benzyl moiety was chosen since it can be selectively cleaved by various reagents, thus allowing nitrogen functionalization. 38 Condensation of 1 with 2-haloaniline 2a or 2b afforded stable enamines 3a and 3b respectively, followed by the quantitative reduction to cis/trans anilinoesters 4a and 4b.…”