New synthesis of 5,6,7,8‐tetrahydro‐4H‐thieno[2,3‐d]azepine

Abstract

This paper describes two new access routes to 5,6,7,8‐tetrahydro‐4H‐thieno[2,3‐d]azepine from 2‐(2‐thienyl)ethylamine or its N‐(2‐chlorobenzyl) derivative. One of these two syntheses involves a new ring expansion from a 6,7‐dihydro[3,2‐c]pyridinium derivative, chloromethylated in position 4.

Asymmetric Total Synthesis of Vindoline

“…Formation of the primary tosylate 26 (TsCl, DMAP, Et 3 N, CH 2 Cl 2 , 25 °C, 16 h, 93%) and its subjection to conditions developed for ring expansion18 (NaOAc, dioxane–H 2 O, 70 °C) provided the key 6-membered ring ketone 17 (61%). Although several mechanistic possibilities can be envisioned for this transformation, some of which proceed through an aziridiniumion, it is most simply and formally represented as hydrolysis of the N,O -ketal to release a reactive α-tosyloxymethyl ketone followed by its intramolecular N -alkylation to provide the 6-membered ketone 17 (equation 2).…”

A short synthesis of praziquantel

“…isoquinoline as the starting material has been described only in patents, a more direct route was desired for production on a n industrial scale. Two other different approaches have also recently been described in the literature [4,5].…”

“…We now wish to report a related synthesis in which the basic strategy for the construction of the tricyclic framework, the selective reduction of the imide function in a piperazine-2,6-dione followed by cyclization in acidic medium, is the same as reported [4]. However, the preparation of the suitably protected l-phenethyl-2,6-piperazinedione was carried out by a more direct route in which the commercially available N-benzyliminodiacetic acid was the starting material.…”