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Please login to access the full content or check if you have access via25.6.6.2 Method 2: Intramolecular Formylation with Formic Esters: Lewis Acid Mediated Formylation of Phenols by Fries Rearrangement of Aryl Formates
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Schall, A.; Reiser, O., Science of Synthesis, (2007) 25, 606.
Aryl formates can act as intramolecular formylating agents via a Fries rearrangement (Table 1).[9] Due to the instability of formylium cations, conditions must be chosen that sufficiently activate the aryl formate without causing its decomposition. Consequently, the choice of Lewis acid is crucial for the success of the rearrangement. As found for transformations using formyl fluoride (Section 25.6.6.3), boron Lewis acids give the best results here for the formation of 2-hydroxybenzaldehydes 4, while aluminum trichloride apparently does not give sufficiently stable Lewis acid adducts with aryl formates but more likely unstable formylium ions, resulting largely in the decomposition of the starting materials (Scheme 3).
Meeee 8 8-Meeeeeeeeeeeeeeeeeee eeee Meee Meeeeeee[8]
M8 | M8 | M8 | M8 | Meeeeeeeee | Meeee (%) | Mee |
---|---|---|---|---|---|---|
M | MMe | M | M | MMe8 (8.8 eeeee), 8,8-eeeeeeeeeeeeee, −88 ee 88°M, 8.8 e | 88 | [8] |
M | MMe | M | M | MMe8 (8.8 eeeee), 8,8-eeeeeeeeeeeeee, −88 ee 88°M, 88 e | 88 | [8] |
M | MMe | M | MMe | MMe8 (8.8 eeeee), 8,8-eeeeeeeeeeeeee, 8 ee 88°M, 8 e | 88 | [8] |
M | MMe | MMe | M | MMe8 (8.8 eeeee), 8,8-eeeeeeeeeeeeee, −88 ee 88°M, 8 e | 88 | [8] |
eMe | M | M | Me | MMe8 (8.88 eeeee), MeMe8 (8.88 eeeee), eeeeeeeeeeeee, 88°M, 8.8 e | 88e | [8] |
eMe | M | M | Me | MMe8 (8.88 eeeee), MeMe8 (8.88 eeeee), eeeeeeeeeeeee, −88 ee 88°M, 88 e | 88 | [8] |
Me | M | M | eMe | MMe8 (8.8 eeeee), MeMe8 (8.8 eeeee), eeeeeeeeeeeee, −88 ee 88°M, 8 e | 88 | [8] |
Me | Me | M | Me | MMe8 (8.88 eeeee), MeMe8 (8.8 eeeee), eeeeeeeeeeeee, −88 ee 88°M, 88 e | 88 | [8] |
Me | Me | M | Me | MMe8 (8.88 eeeee), eeeeeeeeeeeee, −88 ee 88°M, 88 e | 88 | [8] |
e Meeee eeeeeeeeee ee 8M MMM.
Meeeee 8 Meeee Meeeeeeeeeeee ee 8-Meeeeeee Meeeeee ee 8-Meeeeee-8-eeeeeeeeeeeeee[8]
Meeeeeeeeeee Meeeeeeee
8-Meeeeee-8,8-eeeeeeeeeeeeeeeeeeeee (8, M8 = M8 = M; M8 = M8 = MMe); Meeeeee Meeeeeeee:[8]
M eeee ee MMe8 (88 eM, 8 eee) ee 8,8-eeeeeeeeeeeeee eee eeeee eeeee eee eeeeeee ee e eeee ee 8,8-eeeeeeeeeeeeeee eeeeeee (8.88 e, 8.888 eee) ee 8,8-eeeeeeeeeeeeee (88 eM). Mee eeeeeee eee eeeeeee eee 8 e ee 88°M. Meeee eeeeeeeeee eeee M8M (888 eM) eee eeeeeeeeee, eee eeeeeee eeeee eee eeeeee eeee M8M (88 eM), eeeee (Me8MM8), eee eeeeeeeeeeee eeeee eeeeeee eeeeeeee (88 Meee). Meeeeeeeeeeeeeeee ee eee eeeeeee (M8M/eMeMM 8:8) eeee eee eeeeeee; eeeee: 8.88 e (88%); ee 88°M.
References
[9] | Meeeeee, M.; Meee, M.; Meee, M.; Meeeeeeeee, M., M. Meeeeeeeeee., M, (8888) 88, 8888. |