Regioselective ortho-functionalization of bromofluorenecarbaldehydes using TMPMgCl·LiCl

Abstract

A highly regioselective functionalization of 7-bromofluorene-2-carbaldehydes, potent organic chromophores, in position C3 using a mild ortho-metallation strategy (DoM) with TMPMgCl·LiCl has been developed. This approach allows the preparation of highly functionalized fluorene derivatives by conversion of the in situ generated metalated species with various electrophiles giving a fast access to novel organic phosphorescent dyes.

Clickable azide-functionalized bromoarylaldehydes – synthesis and photophysical characterization

“…Conversion to the 2-aryloxazoline 17 was accomplished in 92% yield using the same method as described for the synthesis of 6 and 10 . ortho -Metalation with TMPMgCl·LiCl [ 70 ] and conversion of the magnesiated species with DMF to carbaldehyde 18 was followed by reduction with NaBH 4 to give the primary alcohol 19 . In contrast to benzaldehyde 7 , carbaldehyde 18 showed no decomposition at ambient temperature.…”

“…Double bromination to 14, followed by double methylation of the methylene bridge to 15 and a lithiation/formylation sequence afforded 7-bromofluorene-2-carbaldehyde 16 in excellent yield over three steps. Conversion to the 2-aryloxazoline 17 was accomplished in 92% yield using the same method as described for the synthesis of 6 and 10. ortho-Metalation with TMPMgCl•LiCl [70] and conversion of the magnesiated species with DMF to carbaldehyde 18 was followed by reduction with NaBH 4 to give the primary alcohol 19. In contrast to benzaldehyde 7, carbaldehyde 18 showed no decomposition at ambient temperature.…”

“…Our group is highly interested in the de novo synthesis of small organic luminophores and in this regard, we recently developed efficient methods for the synthesis of ESIPT-based luminophores [ 70 – 72 ]. Herein, we present the efficient functionalization of derivatives of the potent luminophores 1 and 2 with “clickable” azide functionalities to target the structures 3–5 and further investigated the influence of this functionalization, both in the unlinked azide state and the linked triazole state, on the emission properties of these compounds ( Fig.…”

Clickable Azide-Functionalized Bromo-Aryl-Aldehydes – Synthesis and Photophysical Characterization

“…Triplet state excitons are generated by the spin-forbidden intersystem crossing (ISC) process from the first excited singlet state (S1). Pursuant to the El-Sayed rule (see Scheme 1b) [22,23], ISC is spin allowed from 1 (n, π*) to 3 (π, π*) and from 1 (π, π*) to 3 (n, π*) excited states, while ISC is spin-forbidden from 1 (n, π*) to 3 (n, π*) and from 1 (π, π*) to 3 (π, π*) excited states, owing to poor orbital overlap, resulting in decreased spin-orbit coupling. Quenching processes of triplet states, induced by molecular motions, oxygen or humidity, restrict the versatile application of such organic materials [24].…”

“…Our group is highly interested in the de novo synthesis of small organic luminophores and in this regard we recently developed efficient methods for the synthesis of ESIPTbased luminophores [70,71]. Herein, we present the efficient functionalization of derivatives of the potent luminophores 1 and 2 with "clickable" azide functionalities to target structures 3-5 and further investigated the influence of this functionalization, both in the unlinked azide state and the linked triazole state, on the emission properties of these compounds (Figure 1).…”