Cyclopropyl Building Blocks for Organic Synthesis, 42. An Unprecedented Mode of Ring Opening of Methylenecyclopropane Moieties – Reactions of Methylenecyclopropanecopper Reagents with an Electrophilic Glycine Equivalent

✍ Scribed by Kozhushkov, Sergei I. ;Brandl, Melanie ;Yufit, Dmitrii S. ;Machinek, Reinhard ;de Meijere, Armin

• Book ID: 102902596
• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 787 KB
• Volume: 1997
• Category: Article
• ISSN: 0947-3440
• DOI: 10.1002/jlac.199719971105

✦ Synopsis

Abstract

The reactions of ethyl 2‐acetoxy‐2‐diphenylmethyleneaminoacetate (1) with organocopper reagents derived from bicyclopropylidene (2) and methylenecyclopropane (3) are accompanied by an unusual mode of opening of one three‐membered ring to give 4‐methylene‐1,2,3,4‐tetrahydropyridine derivatives 8a, 9 in good yields. The cuprate derived from methylenespiropentane (4) reacts with 1 to yield both the normal substitution product 14 (37%) as well as the rearrangement product 15 (34%), while the simple cyclopropylcuprate undergoes substitution to give the protected cyclopropylglycine 16 (75%) without rearrangement. The tetrahydropyridine 8a shows an interesting tautomerism in solution. The 4‐cyclopropylidenetetrahydropyridine 15 undergoes an unusual dehydrodimerization to produce two separable rotamers, C~2~‐19 and C~1~‐19, via 18.