New methods and reagents in organic synthesis. 75.  asymmetric synthesis of α-hydroxy ketones using chiral phase transfer catalysts

Masui, Masao; Andõ, Akira; Shioiri, Takayuki

doi:10.1016/0040-4039(88)85224-9

Cited by 143 publications

(41 citation statements)

References 5 publications

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“…In most cases they are reduced in situ to the corresponding alcohols [3] or decomposed to give other products depending upon the nature of the substrate and the reaction conditions [25,34,361. An especially noteworthy development is Shioiri's catalytic enantioselective autoxidation process which allows a-hydroxyketones to be obtained (after in situ reduction of the hydroperoxides) in high yields and reasonable optical purity (Scheme 15) [37].…”

Section: Autoxidation Of Curbonyl Compoundsmentioning

confidence: 99%

Peroxyl Radicals in Synthesis

Boukouvalas¹,

Haynes²

2001

Radicals in Organic Synthesis

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This chapter covers organic compounds prepared via intermediates which are alkyl peroxyl radicals (ROO') generated either by addition of ground state (triplet) oxygen to carbon-centered radicals, or by hydrogen atom abstraction from the corresponding hydroperoxides (ROOH). While some earlier work is briefly mentioned, the focus is primarily on new developments, published over the past decade or so. The emphasis is heavily on synthetic applications rather than physical, biological and environmental aspects of peroxyl radical chemistry. A book exclusively devoted to the latter topics has recently been published [l]. Some preparatively relevant pathways involving peroxyl radicals have been previously discussed in the context of reviews on the oxidation of organic molecules [2-41 and the synthesis of organic peroxides [5][6][7][8]. The present survey is clearly distinguished in scope; it is intended to cover a more diverse array of peroxyl radical pathways and to highlight recent applications in the field of natural product synthesis. The aim is to alert not only the peroxide specialist, but also the synthetic chemist in general, since the first-formed peroxidic products can be used as relay intermediates in the synthesis of nonperoxidic compounds. Autoxidation of HydrocarbonsThe oxidation of hydrocarbons and other organic molecules with oxygen or air is usually referred to as autoxidation [4, 7a, 91. This entirely atom-economical process (Eq. 1, Scheme 1) is ca. 18-24 kcal/mol exothermic and irreversible at temperatures below 250°C. Although the initiation step (Eq. 2) is not well understood [2, lo], it is clear that a chain radical process is involved, with addition of molecular oxygen to R as the initial propagation step (Eq. 3 ) . At oxygen pressures above 100 mm Hg, the reaction of R' with 0 2 proceeds with rate constants approaching the diffusioncontrol limit [7a, 9a]. The second propagation step involves hydrogen atom abstrac- Radicals in Organic Synthesis Edited

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Section: Autoxidation Of Curbonyl Compoundsmentioning

confidence: 99%

Peroxyl Radicals in Synthesis

Boukouvalas¹,

Haynes²

2001

Radicals in Organic Synthesis

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“…19 Many synthetic methods have been developed for the preparation of chiral a-hydroxyketones, 19 -22 and their absolute configurations have been determined by stereoselective reactions, 23,24 by spectroscopic methods such as Mosher methods, 19 or by comparison of optical rotation/ CD with known compounds. 25,26 Although these methods have been used in various specific cases, they are not general enough to be applicable to all a-hydroxyketones, such as closely related hydroxyketones that Merck synthesized as part of this program. For example, in at least one case an assignment was tentatively made based on similar retention times by chiral HPLC.…”

mentioning

confidence: 99%

Chiral recognition of cyclic α‐hydroxyketones by CD‐sensitive zinc tetraphenylporphyrin tweezer

Ishii¹,

Chen²,

Miller³

et al. 2005

Chirality

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A combined chemical/chiroptical microscale protocol for the determination of absolute configurations of cyclic alpha-hydroxyketones is described. The hydroxyl group in cyclic alpha-hydroxyketones is converted into (3-aminopropylamino)acetate (NH2CH2CH2CH2NHCH2COOR), or more generally, according to a newly developed protocol, into (3-hydroxypropylamino)acetate group (HOCH2CH2CH2NHCH2COOR). The resultant conjugated compound forms a 1:1 host-guest complex with a dimeric zinc porphyrin tweezer, which exhibits exciton-coupled bisignate CD spectrum centered around the 420-nm porphyrin Soret band due to induced helicity between the two porphyrins in the complex. The absolute configurations of the alpha-stereogenic center is then determined by comparison of the sign of the observed CD exciton couplet of the complex with that of the preferred porphyrin twist predicted by the Merck Molecular Force Field (MMFFs) method.

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“…26 It was later shown that this method was also successful in the hydroxylation of oxindoles. 27 A recent diastereoselective a-hydrogenation with molecular oxygen employed chiral auxiliary-based amides to form enolates with sodium hexamethyldisilazane (NaHMDS) (Scheme 14).…”

Section: Oxygen As Oxidantmentioning

confidence: 98%