Scalable Synthesis of Naphthothiophene and Benzodithiophene Scaffolds as π-Conjugated Synthons for Organic Materials

Abstract

The synthesis on a gram-scale and the full characterization of naphtho[1,2-b]thiophene and benzo[1,2-b:6,5-b']dithiophene 4-carboxylate esters bearing 2-octyldodecyl side chains, and their stannylated and brominated derivatives, suitable for their insertion into π-conjugated polymers is described. The fully soluble and processable synthons are obtained through a cascade sequence of reactions, namely direct arylation and cross aldol condensation, which create an effective pathway for the annulation and π-extension of suitable, commercially available reagents. The newly reported synthesis are compared, whenever possible, using ‘green chemistry metrics’ with literature synthesis, showing dramatic improvements.

Aminothiaindanone as an Accessible Scaffold for a Three-Point Chemical Diversity

“…Moreover, synthetic access to this scaffold remains relevant as can be seen from recent works in carbonylation, 26 in carbocyclization, [27][28][29] direct functionalization 30,31 or in annulation of thiophene heterocycles. [32][33][34][35] Therefore, the present study has been done to explore the possible functionalization of aminothiaindanone scaffold with three diversity points: first on the thiophene ring, second on the amine group, and finally third on the ketone part of the scaffold.…”

“…The synthetic pathway was adapted from an earlier work of our laboratory using different reagents to optimize the protocols. 33,34 3-Amino-3-(2-thienyl)propanoic acid (4) was synthesized from commercial thiophene-3carboxaldehyde using the Rodionow-Johnson reaction, which allows to obtain directly -amino acids from the aldehydes by reaction with malonic acid and ammonia. 37 The -amino acid 4 was isolated in modest yield (30%) due to the formation of known by-products, that is, 2-(2-thienylmethylene) malonic acid and 3-(2-thienyl)acrylic acid.…”

Scalable Synthesis of Naphthothiophene-based D-π-D Extended Oligomers through Cascade Direct Arylation Processes

“…16 Furthermore, a protocol for the synthesis of benzodithiophene (BDTb) and naphthothiophene (NT) compounds, having C 20 alkyl chains for solubilization purposes, was optimized for their gram-scale production. 17 The interesting properties of compounds 1 and 2, together with their sustainable and scalable synthesis, can lead to a new class of oligomers for OPV applications.…”

“…20 We screened optimal reaction conditions for DHA using 2 equivalents of 2-octyldodecyl naphtho[1,2-b]thiophene-4-carboxylate (1; Table 1), which was synthesized in one step as previously reported. 17 Table 1 Direct Arylation Reaction using Substrate 1 and 3 21,22 Initial attempts were performed under classical conditions for DHAs; namely, Pd(OAc) 2 as the catalyst and K 2 CO 3 as the base (Table 1, entry 1). After 24 h, substantial amounts of unreacted reagents 1 and 3 were recovered by flash chromatography, along with traces of target compound 4a and byproduct 4c, resulting from dimerization of 1 (Scheme 2).…”

“…Compound 5 was obtained by bromination of 1 with N-bromosuccinimide (NBS) in CHCl 3 at room temperature. 17 Direct arylation was performed using substrates 2 and 5 with the same protocol reported in Table 1, entry 5. Compound 6 was isolated in 87% yield after a troublesome purification, due to severe spot broadening and molecular aggregation using silica gel for chromatography and apolar solvents as the eluting phase.…”