&lt;strong&gt;Synthesis of naphthothiophene derivatives through polar Diels-Alder reactions employing 5-nitrobenzothiophene as electrophile. Microwave irradiation vs classical thermal conditions&lt;/strong&gt;

Claudia Della Rosa

doi:10.3390/ecsoc-19-c003

Abstract

Herein we report a simple, economical and efficient one-step procedure to synthesize the naphtho[2,1-b]thiophene ring system in good to excellent yield through the polar Diels-Alder reactions of 5-nitro-3-acetylbenzothiophene and dienes of different nucleophilicity. In thermal conditions the reactions were developed in molecular solvents; moreover the reaction system was exposed to microwave irradiation as a complement of reaction conditions.

Highlights

Naphthothiophene has been reported as a promising p-type semiconductor
Its potential in heterocyclic chemistry synthesis is very well known. This process is in one step inter or intramolecular from aspects diene and dienophile bearin an almost unlimited number of variants. 2,3 Recently we have reported a simple scheme to synthesize the dibenzothiophene ring system in good yield through the DA reaction of 2- and 3-nitrobenzothiophenes and different dienes.[4]
The study of P-DA reactions was carried out employing 5-nitro-3-acetylbenzothiophene 1a as electrophilic dienophile, whereas 1-methoxy-3-trimethylsilyloxy-1,3-butadiene 2, 1- trimethylsilyloxy-1,3-butadiene 3 and isoprene 4 were chosen as ER diene partners (Figure 1)

Summary

Introduction

Naphthothiophene has been reported as a promising p-type semiconductor. The development of high-performance n-type semiconductors is highly desirable.[1]. The study of P-DA reactions was carried out employing 5-nitro-3-acetylbenzothiophene 1a as electrophilic dienophile, whereas 1-methoxy-3-trimethylsilyloxy-1,3-butadiene 2, 1- trimethylsilyloxy-1,3-butadiene 3 and isoprene 4 were chosen as ER diene partners (Figure 1). Exposure of 1a to 1-trimethylsilyloxy-1,3-butadiene 3 (150oC and 120oC, 72 h, Bz anh) afforded naphthothiophene 6 with reasonable yield (53% and 50%).

Results

Conclusion