A Convenient 5-exo-dig Cyclization Route to Diastereomerically Pure Methyl (2S)-2-(1-benzyl-3-oxo-1,3-dihydro-2H-isoindol-2-yl)-3-methylbutanoate

One-pot access to 2-oxazolines via a Castro-Stephens coupling and intramolecular cyclization

Aim:

Here, we have reported easy one-pot access to a series of oxazolines using a modified Castro-Stephens coupling protocol.

Background:

2-oxazolines have been shown to have significant biological activity and wide-ranging applications in organic chemistry. These properties make oxazolines as heterocyclic compounds of immense importance.

Objective:

The objective of this study is to synthesize oxazoline derivatives via an economical and one-pot protocol.

Method:

2-oxazoline has been synthesized through Cu-powder mediated Castro-Stephens coupling and intramolecular cyclization route. The mechanism involves a rearrangement in which one of the oxygen from the N-acylamino alcohol group is liberated as water and then transferred to alkyne functionality to form 2-oxazoline derivatives. The oxazolines were characterized by NMR, mass, and XRD studies.

Result:

The protocol is economically viable and uses readily available Cu-powder along with DMF for cross-coupling and cyclization steps.