Indanols, formation

Meador, M.A. and Wagner, P.J. (1983) 2-Indanol formation from photo-cyclization of a-arylacetophenones. Journal of the- American Chemical Society, 105, 4484-4486. 

The indanols 44 and 45 can only be the products of a formal [4 + 2] cycloaddition23 of the vinylketene complex 42.a with 1-pentyne. Note that upon reaction of 42.b with diethylpropynylamine a formal [2 + 2] cycloaddition65 is seen to take place, yielding the cyclobutenone 47 along with a tricarbonylchromium complex, tentatively identified as 48.66,67 As one would expect, the vinylketene complex 42.b underwent 1,2-additions with pyrrolidine and sodium methoxide in methanol, yielding 49 and 50, respectively. The CO-insertion step leading to vinylketene formation is reversible in some systems,51,68,69 but there is no evidence of this for complex 42.a. Heating a benzene solution of complex 42.a at 80°C under an atmosphere... 

A similar solvent trapping mechanism has been proposed to account for formation of 5-indanol from acid-catalyzed isomerization of the arene oxide tautomer of oxepin (22) (73JA60641). 

Co-oxidation of indene and thiophenol takes place readily if the reactants in benzene solution are shaken with oxygen at temperatures in the range 20° to 40°C. (7). The major primary product has been shown to be frans-2-phenylmercapto-1 -indanyl hydroperoxide, I, which rearranges spontaneously to the two racemes of frans-2-phenylsulfinyl-l-indanol, II (8), and a tentative reaction scheme involving a three-step radical chain based on the suggestion of Kharasch, Nudenberg, and Mantell (11) was proposed for the formation of I. These three products accounted for 86% of the oxygen absorbed. 

Enantiomerically pure d.v-1 -amino-2-indanol and its derivatives have been used as ligands in numerous catalytic asymmetric carbon-hydrogen, carbon-carbon, and carbon-heteroatom bond formation reactions. The conformationally constrained indanyl platform has emerged as a particularly valuable backbone in a variety of catalytic processes leading to high levels of asymmetric induction. The aminoindanol 1 has also been used as a resolution agent (Chapter 8) as well as a chiral auxiliary (Chapter 24). For the synthesis of 1 see Chapter 24. 

Isomers of ris-l-amino-2-indanol have attracted considerably less attention, although improved asymmetric inductions have been reported on several occasions. Diethylzinc addition to aldehydes with m-.V-disubslil tiled-1 -amino-2-indanols as catalysts yielded secondary alcohols with low enantiomeric excesses (40-50%),37 whereas r/.v-N-disubstituted-2-amino-1 -indanols led to increased selectivities (up to 80% ee) (see Section 17.3.2).46 High degrees of enantioselection were eventually achieved in the addition of diethylzinc to aliphatic and aromatic aldehydes with /raw.v-N-dialkyl-l-substituted-2-amino-l-indanols as catalysts (Scheme 17.25).47 Optimal results were obtained with bulky groups at the hydroxy-bearing carbon and at the nitrogen (R = Ph, R1 = ft-Bu), which led to the formation of (R)-l-phenylpropanol in 90% yield and 93% ee. 

The biradical corresponding to 16a produces indanol 18 quantitatively, whereas the biradical from 16b undergoes disproportionation to form mainly 19. The quantum efficiency for the formation of 18 was 0.03 in hydrocarbon solvent, and 1.0 in methanol. In contrast, the total quantum yield for 16b was rather low (0.02-0.05) in both hydrocarbon and methanol solvents. These differences were ascribed to a considerably smaller dihedral angle between the carbonyl and t-butyl benzene in the triplet excited state of 16a in comparison to 16b, and a differing rotational freedom in the biradical 17 intermediate species. 

The same group [7] has further reported the formation of two diastereomeric sets of indanols (23Z, 23E) and (24Z, 24E) from the irradiation of o-tert-amylbenzophe-none (20), depending upon the regioselectivity of H-abstraction. (Scheme 8.5). 

Scheme 5.50 Proposed catalytic cycle for the formation of indanol.

Scheme 5.51 Formation of indanols and indanones by p-carbon elimination of tert-cyclobutanol.

With this new methodology in hands, Hu et al. [166] explored the trapping of the 1,4-addition intermediate with a different electrophile for the development of a new MCR. RhjCOAc) was again the most active catalyst in the 1,4-addition/aldol-type intramolecular cascade reaction. Under the optimized reaction conditions, this three-component reaction worked well with a broad family of bifunctional substrates 135 bearing different substituents on the aryl group next to the enone moiety and a variety of alcohols 136 (Scheme 3.63). In all cases, 1-indanols 137 were obtained in 60-83% yield and with complete diastereoselectivity. Enantiopure 1-indanol was obtained employing a L-menthol-derived diazo compound. The intermolecular four-component version was also attempted, but the formation of the desired product was not observed. 

Figure 7.9 The side reactions occurring during the condensation of phenol with acetone. The formation of o.p-BPA isomers (1), mesityl oxide (2), the chromans (3 and 4). trisphenol (5). l,1.3-trimethyl-5-indanol (6), alkylated phenols (7) and 2,2.4-trimethylchromen (8) [40,41,43,45).

Shigeno, M. Yamamoto, T. Murakami, M. Stereoselective Restructuring of 3-Arylcyclobutanols into 1-Indanols by Sequential Breaking and Formation of Carbon-Carbon Bonds. Chem. 2009,15,12929-12931. 

Shigeno M, Yamamoto T, Murakami M (2009) Stereoselective restructuring of 3-arylcyclobutanols into 1-indanols by sequential breaking and formation of carbon-carbon bonds. Chem-Eur J 15(47) 12929-12931. doi 10.1002/chem.200902593... 

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