Indanone rearrangement

The Fries rearrangement can be viewed as a type of Friedel-Crafts acylation reaction. Two examples of this reaction are given in Scheme 5.1-61. The first is the rearrangement of 4,4 -diacetoxybiphenyl to 4,4 -dihydroxy-3,3 -diacetoxybiphenyl in a NaCl/AlCl3 (X(A1C13) = 0.69) molten salt [93]. The second example is the rearrangement of phenyl 3-chloropropionate to 2 -hydroxy-3-chloropropiophenone, followed by cyclization to an indanone [94]. 

Scheme 10.3 gives some examples of pinacol and related rearrangements. Entry 1 is a rearrangement done under strongly acidic conditions. The selectivity leading to ring expansion results from the preferential ionization of the diphenylcarbinol group. Entry 2, a preparation of 2-indanone, involves selective ionization at the benzylic alcohol, followed by a hydride shift. 

Lee and coworkers ", studying the Beckmann rearrangement of 1-indanone oxime derivatives 240, observed that the pure E and Z oximes isomerize under mild acidic conditions such as silica gel (equation 72). In the presence of Brpnsted or Lewis acids as silica gel or AICI3 the high rotational barrier of C=N double bond would be lowered by the formation of a complex between the tosylate and AICI3 241. This fact makes the... 

The Beckmann rearrangement of oxime esters is catalysed by Brpnsted or Lewis acids and these conversions are usually non-stereospecific, as demonstrated by the studies of Beckmann rearrangement of 1-indanone oximes derivatives 240a with aluminium chloride as a catalyst " (equation 88). 

The stereoselectivity of the acidic rearrangement of indanone oximes 378 into the carbostyril core was found to be dependent on the substiments of the aromatic ring (equation 150). Moderate yields were observed. 

Aromatic hydroxylation.1 The reaction of l-isopropylidene-2-indanone (1) with singlet oxygen (Rose bengal) in CH3CN at —35° results in an unstable product 2. which on deoxygenation with P(OC2Hs)3 affords the phenol 3 in 55% yield. The initial reaction is presumed to form an endoperoxide (a) by a [4+2]cycloaddition, which rearranges to 2. 

Several isothiochroman-4-ones rearrange photochemically to thio-chroman-3-ones (61) via the intermediate spiro-thietan-3-one (62) [Eq. (27)] 248,249 yjj(j jg transformed into l-indanone ° photochemically. 

The epoxide 131 rearranges to afford a-hydroxyethylene-2-indanone (132) in moderate yield when heated under reflux in LiC104-toluene (Sch. 67). The proposed mechanism is lithium ion-promoted epoxide cleavage then 1,2-aryl migration to afford a relatively stable oxonium ion which cleaves to furnish a benzylic carbocation with subsequent 1,2-hydride shift affording the yS-ketoaldehyde. An attempt to bring about this transformation with BF3 OEt2 proved problematic [116]. 

Migration of the carbonyl during epoxide cleavage is used to produce hydroxy lactones from epoxides of carboxylic acids (Eq. 44) [84]. a-Acyl-2-indanones [85], furans [86], and A -oxazolines [87] (Eq. 45) can also be synthesized by cleavage and rearrangement of epoxides with BF3 Et20. 

During the total synthesis of (+)-fredericamycin A, the spiro 1,3-dione center was introduced by R.D. Bach et al. utilizing a mild mercury-mediated semipinacol rearrangement that involved a [1,2]-acy shift. The indanone dithioacetal was reacted with 1,2-b/s[(trimethylsilyl)oxy]cyclobut-1-ene in the presence of mercuric trifluoroacetate and the rearrangement took place in situ. 

Aiyl esters such as those of a-halopropionic and a-halobutyric acids undergo cycloalkylation reactions, probably via preliminary Fries rearrangement to 3-halohydroxy ketones, giving the corresponding substituted indanones (equation 98). ... 

Similarly, rearrangements of benzoylcyclopropanes catalyzed by aluminum trichloride at 100 "C produced indanones. ... 

The total synthesis of dihydrolycorine (38), the sole hydrogenation product of lycorine (6 R1 + R2 = CH2, R3 = R4 = H) and an alkaloid in its own right, has been reported.27 Scheme 3 shows how treatment of the Diels-Alder adduct (33) with methanol gave a mixture of two half-esters which were directly subjected to Friedel-Crafts cyclization to give the indanone ester (34) and a rearrangement product. Attempted Schmidt ring expansion on (34) failed, but a prior reduction-oxidation sequence followed by treatment with sodium azide and hydrolysis produced the desired lactam (35) and an isomeric compound whose structure remains undetermined. Lactam (35) was readily converted into a chain-extended... 

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