Synfacts 2015; 11(1): 0040
DOI: 10.1055/s-0034-1379672
Synthesis of Materials and Unnatural Products
© Georg Thieme Verlag Stuttgart · New York

An Unusual Regioselective Di-, Tetra-, and Hexa-Bromination

Contributor(s):
Timothy M. Swager
,
Wen Jie Ong
Kohl B, Over LC, Lohr T, Vasylyeva M, Rominger F, Mastalerz M * Ruprecht-Karls-Universität Heidelberg, Germany
Selective Even-Numbered Bromination of Triptycene Tris(thiadiazoles).

Org. Lett. 2014;
16: 5596-5599
Further Information

Publication History

Publication Date:
15 December 2014 (online)

 

Significance

Mastalerz and co-workers report an unusual even-numbered bromination of triptycene tris(thiadiazoles), yielding regioselectively dibromo-, tetrabromo-, and hexabromotriptycenes with two bromines each on the same phenyl ring. These brominated compounds will be useful in the synthesis of π-conjugated polymers of intrinsic microporosity and small electron acceptors.


#

Comment

Given that the C–C bond lengths of the phenyl rings are alternating, and hence the phenyl rings exhibit more olefinic than aromatic character from X-ray single crystal structure of 1, the mechanism for this unusual even-numbered bromination is proposed to involve 1,4-addition of Br2, followed by subsequent re-aromatization of the phenyl ring by oxidation by Br2 or FeBr3. It is also proposed that this 1,4-addition–oxidation sequence is favored over electrophilic aromatic substitution. Furthermore, to demonstrate the utility of these monomers in the synthesis of conjugated polymers, dibromotriptycene 2 has been shown to undergo facile Suzuki–Miyaura cross-coupling.


#
#