DDQ oxidation of hydroxyisochromans and homologues

Abstract

Some hydroxyisochromans and hydroxyphthalans are tested under oxidative conditions obtaining hydroxybenzophenone derivatives. All reactions were followed by (1)H NMR spectroscopy. Some final main oxidation products were also isolated and characterised.

DDQ as a versatile and easily recyclable oxidant: a systematic review

“…In this process, the orthoquinone moiety was converted into the main oxidation product, a hydroxybenzophenone analog originating from C 1 -dibenzylic carbon oxidation to a carbonyl group such as in structures 64, 66, and 68. 54 Not long ago, Hu and co-workers (2013) disclosed a facile and promising protocol for the deprotection of benzyl ether 69 by DDQ-catalysed oxidation (Scheme 30). The reaction was carried out in an open atmosphere along with tert-butyl nitrite (TBN).…”

“…In this process, the orthoquinone moiety was converted into the main oxidation product, a hydroxybenzophenone analog originating from C 1 -dibenzylic carbon oxidation to a carbonyl group such as in structures 64, 66, and 68. 54 …”

Boosting Molecular Complexity with O2: Iron‐Catalysed Oxygenation of 1‐Arylisochromans through Dehydrogenation, Csp3−O Bond Cleavage and Hydrogenolysis

“…A case in point is the oxidation of isochroman and its derivatives, which can lead to products of widely ranging bioactivities but has generally been performed with toxic, expensive and/or environmentally hazardous terminal oxidants, such as CrO 3 /H 2 SO 4 , 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ), ceric ammonium nitrate (CAN), SeO 2 , CrO 3 /H 5 IO 6 and KMnO 4 . Of particular note is the oxidative cleavage of the endocyclic Csp 3 −O bond in 1‐arylisochromans, which has been exploited by medicinal chemists for the synthesis of benzodiazepines, benzodiazepinones and benzodiazepinethiones, analogues of the neuroprotective agent GYKI52466 and the related LY300164 and tofisopam (Scheme A) .…”

“…[7] However,t he development of similarc atalysts for the selective aerobic oxidation of ethers, particularly the oxidative cleavage of ethereal CÀOb onds, has received much less attention, [7c, 8] although such reactions could provide new pathways for the synthesis of bioactive molecules and new insight into the mechanisms of ether degradation by oxygenases and drug metabolism. [9] Acase in point is the oxidation of isochroman andits derivatives, which can lead to products of widely ranging bioactivities but has generally been performedw ith toxic, expensive and/or environmentally hazardous terminal oxidants, [10,11] such as CrO 3 /H 2 SO 4 , [12] 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), [13] ceric ammonium nitrate (CAN), [14] SeO 2 , [15] CrO 3 / H 5 IO 6 [16] and KMnO 4 . [17] Of particularn ote is the oxidative cleavage of the endocyclic Csp 3 ÀOb ond in 1-arylisochromans, which has been exploited by medicinal chemists fort he synthesis of benzodiazepines, benzodiazepinones and benzodiazepinethiones, analogues of the neuroprotective agent GYKI52466 and the related LY300164 and tofisopam (Scheme 1A).…”

Atom Economical, One-Pot, Three-Reaction Cascade to Novel Tricyclic 2,4-Dihydro-1H-benzo[f]isochromenes

“…As reported by Guiso et al, analogs with only one aromatic ring (isochromans) are easily oxidized to lactones. 22 Based on X-ray crystollographic analysis of a sample left at rt in air, the alkyl 2,4-dihydro-1 H -benzo[ f ]isochromenes 3a-3f herein appear to be prone to oxidation via a similar pathway (Scheme 3). 23 …”