Stereoselective synthesis of (.eta.6-arene)Cr(CO)3 complexes possessing a chiral center at the benzylic position

Uemura, Mamoru; Kobayashi, Toshio; Isobe, Kazuo; Minami, Tatsuya; Hayashi, Yûji

doi:10.1021/jo00365a001

Cited by 76 publications

(22 citation statements)

References 5 publications

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“…William R Roush et al report effect of metal carbonyl complexes, specifically the ability of such complexes to enhance the enantioselectivity of the asymmetric allylborations of unsaturated (aryl and propargylic) aldehydes. These reactions were in contrast to the previously reported examples in which the diastereoface selectivity of the metal carbonyl containing chiral substrates that is enhanced [265][266][267][268][269][270][271][272][273][274][275]. The reactions in which metal carbonyl ligand of achiral substrates lead to enhancement of the enantiofacial selectivity of a chiral reagent [276][277][278].…”

Section: Use Of Metal Carbonyl Complexes To Achieve High Enantioseleccontrasting

confidence: 63%

The chemistry of group-VIb metal carbonyls

Kaushik¹,

Singh²,

Kumar³

2012

Eur. J. Chem.

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KEYWORDSThe special interest attached to the chemistry of metal carbonyls arises from several causes. While quite distinct from the metal carbonyls in the organometallic compounds, they differ in physical properties (e.g., their volatility) from all other compounds of the transition metals. Chemically, they constitute a group of compounds in which the formal valency of the metal atoms is zero, and in this respect (apart, perhaps, from the ammoniates of the alkali metals) they are comparable only with the recently discovered compounds. As a class, the carbonyls are reactive compounds, and a number of new types of inorganic compounds have been discovered. In the concepts for new products, performance, product safety, and product economy criteria are equally important. They are taken into account already when the raw material base for a new industrial product development is defined. Since the discovery of nickel carbonyl by Mond and Langer in 1888, the carbonyls of the iron group and of chromium, molybdenum and tungsten have found important technical applications, e.g., in the Mond nickel process, and for the preparation of the metals in a state of subdivision and of purity suitable for powder metallurgy, for catalysts, etc. The reaction mechanism of the processes developed for producing the carbonyls technically has only recently received its interpretations. Within the space of review it is necessary to limit discussion to a few topics. Particular stress has accordingly laid upon (a) the chemical bonding in metal carbonyls, (b) importance of IR and NMR spectroscopy in characterization of metal carbonyls, (c) substitution reactions of G-VIb metal carbonyls, (d) kinetics and mechanism of substitution reactions in metal carbonyls, (e) substituted complexes of G-VIb metal carbonyl, (f) chelate complexes of G-VIb metal carbonyls, (g) uses of G-VIb metal carbonyl complexes and (h) studies done on G-VIb metal carbonyls.

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Section: Use Of Metal Carbonyl Complexes To Achieve High Enantioseleccontrasting

confidence: 63%

The chemistry of group-VIb metal carbonyls

Kaushik¹,

Singh²,

Kumar³

2012

Eur. J. Chem.

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“…21 The more facile elimination in the present case may be related to the fact that a chromium tricarbonyl unit in an arene complex can stabilize a benzylic cation ( 19 in Table 1). 24 Substitution reactions on the chromium tricarbonyl complex of benzyl chloride are 10 5 times faster than on benzyl chloride itself. 24a The benzylic cation 19 (R = alkenyl) derived from alkoxyenyne 15 would be both benzylic and allylic rather than just benzylic (R = alkyl) as in previous reactions where base was employed to effect o -quinone methide formation which was presumably initiated via base induced deprotonation in phenol complexes of the type 12 (Scheme 3).…”

Section: Chromenes From Alkenyl Carbene Complexesmentioning

confidence: 99%

“…24 Substitution reactions on the chromium tricarbonyl complex of benzyl chloride are 10 5 times faster than on benzyl chloride itself. 24a The benzylic cation 19 (R = alkenyl) derived from alkoxyenyne 15 would be both benzylic and allylic rather than just benzylic (R = alkyl) as in previous reactions where base was employed to effect o -quinone methide formation which was presumably initiated via base induced deprotonation in phenol complexes of the type 12 (Scheme 3). 21 The fact that base is not needed in the present case could be explained if o -quinone methide formation could be initiated by a chromium induced loss of an alkoxide in the complex 5 (Scheme 2).…”

Section: Chromenes From Alkenyl Carbene Complexesmentioning

confidence: 99%

Simultaneous Synthesis of Both Rings of Chromenes via a Benzannulation/o-Quinone Methide Formation/Electrocyclization Cascade

2011

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A new route to the chromene ring system has been developed which involves the reaction of an α,β-unsaturated Fischer carbene complex of chromium with a propargyl ether bearing an alkenyl group on the propargylic carbon. This transformation involves a cascade of reactions that begins with a benzannulation reaction and is followed by the formation of an o-quinone methide and finally, results in the emergence of a chromene upon an electrocyclization. This reaction was extended to the provide access to by employing an aryl carbene complex. This constitutes the first synthesis of chromenes in which both rings of the chromene system are generated in a single step and is highlighted in the synthesis of lapachenole and Vitamin E.

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“…As the latter ligands contain a prostereogenic aryl group, the preparation of ligands possessing planar chirality is possible. Upon reaction with tricarbonyl(naphthalene)chromium, [58] 16 afforded two diastereomeric chromium compounds with planar chirality, 17 and 18. The diastereomers, which were obtained as best in a ratio of 1:1.33, could be separated by column chromatography to yield the pure stereoisomers.…”

Section: Preparation Of Ligandsmentioning

confidence: 99%

“…Thus, from (R,R)-and (S,S)-1,2-diamino-1,2-diphenylethane diastereomeric ligands 19 and 20 were obtained in 84 and 79% yield, respectively, whereas the two enantiomers of 1,2-diaminocyclohexane afforded 21 and 22 in 64 and 67% yield, respectively (Scheme 7). Finally, tetradentate ligands with axial chirality, 23 and 24, were obtained from (R)-and (S)binaphthylamine in 58 Exchanging the primary amines for ammonia gives access to C 3 -symmetric tripodal tris(sulfonamides) (Scheme 8). [44] These ligands were previously obtained by reaction of the aziridine with ammonia in methanol in a rather sluggish process, tosyl derivative 25 requiring 4 d at 50°C for completion (70% yield).…”

Section: Preparation Of Ligandsmentioning

confidence: 99%