𝔖 Bobbio Scriptorium
✦   LIBER   ✦

Stabilised 2,3-Pyridyne Reactive Intermediates of Exceptional Dienophilicity

✍ Scribed by Stephen J. Connon; Anthony F. Hegarty

Book ID
102175703
Publisher
John Wiley and Sons
Year
2004
Tongue
English
Weight
151 KB
Volume
2004
Category
Article
ISSN
1434-193X

No coin nor oath required. For personal study only.

✦ Synopsis

Abstract

The enhanced dienophilicity of 4‐methoxy, 4‐aryloxy and 4‐thiophenoxy analogues 6−9 of 2,3‐pyridyne (2) relative to 2 itself is reported. The regioselective lithiation of 4‐alkoxy‐ (22, 23 and 25) and 4‐thiophenoxy‐2‐chloropyridine (24) at low temperatures, followed by elimination of lithium chloride affords 4‐alkoxy‐ and 4‐thiophenoxypyridynes, which can be trapped in situ in a [4+2] cycloaddition reaction with furan to give endoxides 28−31 in moderate to good yields (25−58%). In contrast, precursors with a hydrogen (18) or methyl (12) substituent at C‐4 give no evidence for pyridyne formation under these conditions. Attempts to generate 6‐isopropoxy‐2,3‐pyridyne (10) from the low‐temperature lithiation of 2‐chloro‐6‐isopropoxypyridine were unsuccessful due to the instability of the 2‐chloro‐6‐isopropoxy‐5‐lithiopyridine. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

📜 SIMILAR VOLUMES

Aminations of bromo-derivatives of 4-eth
Aminations of bromo-derivatives of 4-ethoxy- and 2,4-diethoxy-pyridine, probably involving a 2,3-pyridyne as intermediate
✍ M. J. Pieterse; H. J. den Hertog 📂 Article 📅 2010 🏛 Elsevier Science 🌐 English ⚖ 443 KB

## Abstract The amination of 3‐bromo‐4‐ethoxypyridine with potassium amide in liquid ammonia yielding 2‐amino‐4‐ethoxypyridine as chief product has been reinvestigated. It is shown that 2‐amino‐5‐bromo‐4‐ethoxypyridine is formed as a byproduct, probably __via__ 3,5‐dibromo‐4‐ethoxypyridine and 5‐br