Bamford‐Stevens and Shapiro Reactions in Organic Synthesis

Abstract

Total synthesis of natural products often requires installation of double bond without adding carbon. Bamford-Stevens and Shapiro reactions offer an option to execute such transformation. Several developments have been made in these reactions and their applications in a diverse area of chemistry. Lack of a dedicated review on these reactions in the recent time is hampering an access to collective information and a critical analysis of the new developments. This minireview highlights methodological developments and applications of Bamford-Stevens and Shapiro reactions in organic synthesis published in the past ten years.

Electrochemical Synthesis of Pyrazolines and Pyrazoles via [3+2] Dipolar Cycloaddition

“…This leads to decomposition of the substrate similar to Bamford-Stevens type reactions. [43] In a similar way, acylsubstituted pyrazoline 8 o is not accessible using this method. The hydrazone can undergo oxidative cyclization to an azomethine imine intermediate, which is then subjected to further reactions.…”

Elektrochemische Synthese von Pyrazolinen und Pyrazolen via [3+2] dipolarer Cycloaddition

“…Boronsäuren (4 f 62 %) und Phosphonate (4 l 44 %) werden ebenso toleriert wie heterocyclische Alkene ( 4 Dies führt zu einer Zersetzung des Substrats, analog zu Bamford-Stevens-artigen Reaktionen. [43] In ähnlicher Weise ist das acylsubstituierte Pyrazolin 8 o mit dieser Methode nicht zugänglich. Das Hydrazon kann oxidativ zu einem Azomethiniminzwischenprodukt cyclisiert werden, das im Anschluss weitere Reaktionen unterläuft.…”

Synthetic and Mechanistic Investigation of an Unexpected ­Intramolecular 1-5 Nitrogen to Carbon Tosyl Migration

“…Despite the reported reactivity of the dimedone C-2 position, and the general assumption that indazolone cyclization occurs via a C-2 acylated intermediate, 18 the formation of N,N-acyltosyl hydrazide in the presence of acid anhydrides and Et3N has been reported. 20 However, given the reported lability of tosylhydrazones under strongly basic conditions, 21,22 the survival of compound 8 intact, was unexpected. We reasoned that interrogating the circumstances leading to the formation and isolation of amide 8 would assist in the successful adaptation of Therefore, we reasoned that amide 8 could form through either direct acetylation of the hydrazone N-9, or through Pathway 1, where tetrahedral intermediate 9a collapses into 11a and finally forming amide 8 following workup.…”