Azidophosphonium salt-directed chemoselective synthesis of (E)/(Z)-cinnamyl-1H-triazoles and regiospecific access to bromomethylcoumarins from Morita-Baylis-Hillman adducts.

Soundararajan Karthikeyan,J Helen Ratna Monica,Radha Krishnan Shobana,Ayyanoth Karthik Krishna Kumar,Kamarajapurathu Raju Subimol

doi:10.3762/bjoc.16.130

Soundararajan Karthikeyan, J Helen Ratna Monica + Show 3 more

Open Access

https://doi.org/10.3762/bjoc.16.130

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Abstract

The direct transformation of Morita–Baylis–Hillman (MBH) adducts into molecules of interest is a crucial process wherein allylic hydroxy-protected or halogenated MBH adducts are commonly preferred. Herein, we report an azidophosphonium salt (AzPS)-catalysed straight forward protocol for synthesising structurally demanding (E)/(Z)-cinnamyl-1H-1,2,3-triazoles and halomethylcoumarins from MBH adducts. The novel methodology, efficient catalyst, and direct utilization of MBH adducts under mild reaction conditions qualify the reported procedures as powerful synthetic tools.

Highlights

The presence of versatile functional groups in close proximity classifies Morita–Baylis–Hillman adducts as privileged key scaffolds for synthetic organic chemists
In 2014, several organic transformations employed quaternary phosphonium salts as favourable catalysts [36]. Their synthetic utility was confined to catalysis, but they were used as intermediates for the synthesis of 1H-indazoles [37], as promoters for stereoselective rearrangements [38], and as temporary protectors of O,P-acetals [39], which branded them as promising motifs
The most elaborate process in the proposed methodology is the protection and elimination of the allylic hydroxy group. We believe that this crucial strategy could be primarily resolved by a quaternary phosphonium salt

Summary

Introduction

The presence of versatile functional groups in close proximity classifies Morita–Baylis–Hillman adducts as privileged key scaffolds for synthetic organic chemists. Two individual research groups have reported the multistep pathway to access the cinnamyl-1H-1,2,3-triazole derivatives IX from acetates of MBH adducts (Scheme 2) [32,33]. Scheme 2: Synthetic methodologies for triazolations of MBH adducts.

Results

Conclusion