Design and Synthesis of Benzosultine-sulfone as ao-Xylylene Precursor via Cross-enyne Metathesis and Rongalite: Further Expansion to Polycyclics via Regioselective Diels−Alder Reaction

Abstract

Benzosultine-sulfone 5 has been prepared as a o-xylylene or o-quinodimethane precursor by utilization of rongalite. Thermal activation of this hybrid molecule 5 has resulted a new sulfone-based building block 6. Building block 5 is a suitable precursor for the synthesis of unsymmetrically functionalized polycyclics through Diels-Alder (DA) chemistry. The dibromosulfone 24 and benzosultine-sulfone 5 has also been used for the synthesis of various sulfone based unnatural alpha-amino acid (AAA) derivatives.

A Short Synthetic Route to Benzosultine‐sulfone using Rongalite and [2+2+2]‐Cyclotrimerization

“…Having dipropargyl sulfone 10 in hand, attention was focussed towards the synthesis of benzosultine‐sulfone 8 . Earlier, we have reported the synthesis of a hybrid molecule benzosultine‐sulfone 8 by using but‐2‐yne‐1,4‐diacetate 5 as starting material in eight steps with an overall yield of 7% . Later, we also reported the synthesis of benzosultine‐sulfone 8 via [2+2+2]‐cyclotrimerization of dipropargyl ether 6 and 1,4‐dibromo‐2‐butyne 7 in the presence of Mo(CO) 6 in five steps with an overall yield of 16% (Scheme ) …”

(E,E)‐1,2,3,4‐Tetracyclopropylbuta‐1,3‐diene: Synthesis and Some of Its Properties

“…In spite of the overall steric congestion in ( E , E )‐1,2,3,4‐tetracyclopropylbuta‐1,3‐diene ( 3 ), it readily undergoes Diels–Alder reactions with dimethyl acetylenedicarboxylate (DMAD; 6 ) and N ‐phenylmaleimide ( 7 ), albeit only after extended heating (22 h) in toluene at 130 °C (Scheme ). For comparison, butadiene17a and 2,3‐dimethylbutadiene17b,17c react with DMAD at ambient temperature or at 70–80 °C, respectively. The products 8 and 9 were isolated in 70 % yield each, and both were formed as single diastereomers, as indicated by their NMR spectra as well as by an X‐ray crystal structure analysis of 9 (Scheme ) 9…”

Diversity-Oriented Approaches to Polycycles and Heterocycles via Enyne Metathesis and Diels–Alder Reaction as Key Steps

“…We have also reported the generation of dienes starting with protected, but-2-yne-1,4-diol derivatives 137 by CEM under ethylene atmosphere (Scheme 37). 25 The acyl-protected diene 138a is a suitable starting material to assemble benzoannulated compound 139 , which can be further utilized for the synthesis of polycyclic compounds through a regioselective DA reaction of the benzosultine-sulfone building block 140 . The DA reaction of tosyl-protected diene 138b with various dienophiles under different conditions was unsuccessful.…”