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A century old reaction allows the designing of modern electronic materials

The Vilsmeier-Haack reaction, which is named after German chemists Anton Vilsmeier und Albrecht Haack, was first reported in 1927 [1] and represents one of the widely used methods for formylation of electron rich aromatics using dimethylformamid and phosphorus oxychloride (93-1543 and 97-8875) [2]. This interaction forms chloromethyleneiminium salt (Vilsmeier reagent) and the subsequent hydrolysis leads to the insertion of aldehyde into the aromatic ring (Fig. 1)

Fig. 1. Vilsmeier-Haack reaction

During the last couple of decades the chloromethyleneiminium salt mediated formylation of heterocycles found an effective application in the highly efficient conjugated aromatic polymers that enabled the rapid progress in the development of organic photovoltaic (OPV) technology as a promising alternative to conventional solar cells [3-4].

The benzodithiophene (BDT) (CAS # 267-65-2) moieties are considered the most attractive building block for donor materials, and various BDT based photovoltaic polymers have been successfully developed [3-8]. The implementation of the Vilsmeier-Haack protocol allows the designing of the highly efficient BDT based organic electronic materials [9-14].

In addition, phosphorus oxychloride is used as a liquid dopant precursor for p-type semiconductors and solar cells to create n-type layers in the thermal diffusion process [15-17].

References:

1.  Chem. Ber. 1927, 60, 119.
2.  Synlett, 2010, 7, 1067.
3.  Chem. Rev. 2016, 116, 7397.
4.  Org. Electron. 2021, 89, 106010.
5.  Nano Select 2022, 3, 233.
6.  J. Mater. Chem. A, 2023, 11, 7053.
7.  Acc. Mater. Res. 2022, 3, 540.
8.  J. Phys. D: Appl. Phys. 2023, 56, 044007.
9.  J. Am. Chem. Soc. 2015, 137, 4414.
10.  J. Am. Chem. Soc. 2017, 139, 4929.
11.  J. Am. Chem. Soc. 2017, 139, 5085.
12.  Nat. Commun. 2019, 10, 519.
13.  J. Am. Chem. Soc. 2020, 142, 15246.
14.  ACS Energy Lett. 2019, 4, 943.
15.  Sol. Energy Mater Sol. Cells, 2002, 72, 315.
16.  Energy Procedia, 2013, 38, 305.
17.  Sol. Energy Mater Sol. Cells, 2020, 206, 110348.

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