Tartaric acid derived 1,2-diols

Addition of the analogous methyltitanium reagent to bcnzaldchydc afforded the addition product with only 59% ee34. Use of the methyltitanium reagent obtained via chiral modification by the tartaric acid derived diol 43, did not lead to an improvement of the enantioselectivity42. 

An enantioselective dibromination of cinnamic alcohols (9) has been developed, which involves a combination of dibromomalonate as the bromonium source, a titanium bromide species as the bromide source, and a tartaric acid-derived diol (20 mol%). Ligand acceleration has been observed in this transformation, which affords the dibromides (11) with <85% ee transition state (10) has been proposed. ... 

Chiral titanium catalysts have generally been derived from chiral diols. Narasaka and colleagues251 developed an efficient catalyst, 406, prepared from TiCl2(OPr- )2 and a (+)-tartaric acid derived 1,4-diol. These authors found that Af-crotonyl-l,3-oxazolidin-2-one (404) reacted with cyclopentadiene in the presence of 10 mol% of 406 to give cycloadduct 405 with up to 91% ee (equation 120)252. 

The vicinal diol cyclic sulfate from dimethyl tartrate undergoes nucleophilic opening to give substituted malate esters., However, for this application diethyl and diisopropyl L-tartrates give superior yields and selectivities. The asymmetric cyclopropana-tion of the 1 -alkenylboronic ester derived from dimethyl L-tartrate (eq 5) is another example where other tartaric acid derivatives surpass the performance of dimethyl tartrate. ... 

In general, the chiral hydride reagent is generated in situ by reaction of a suitable metal hydride with chiral ligands such as alkaloids , sugar derivatives , amino alcohol chiral oxazolines tartaric acid derivatives chiral amines and chiral diols... 

Polymer bound 1,4-diols (23) were obtained by reaction of alcoxylates derived from mono-O-benzylated tartaric acid derivatives (22) and chloromethylated resins and then modification of the resulting polymers. Treatment with TiX4 species gave Ti catalysts 24 (Scheme 6). 

Intramolecular versions of the ene reaction using Lewis acids can be applied to nonconjugated dienes. Thus, 2.8-dienoic acid derivatives lead to cyclohexane systems27. Side products in this conversion stem from intramolecular hetero-Diels-Alder cycloaddition. Chiral Lewis acids, such as titanium alkoxidcs modified with tartaric acid derived chiral diols, lead to asymmetric induction with up to 98% ee27,88. 

Aldolization and related reactions. Tartaric acid-derived acyloxyborane complexes are shown to be useful catalysts for asymmetric aldol reactions. (5)-4-Isopropyl-3-tosyl-l,3,2-oxazaborolidin-5-one is an excellent cataly.st, not only for the aldolization " between a silyl enol ether and an aldehyde it also reduces the products to afford syn-l,3-diols. ... 

Miscellaneous Diol-Protected Tartaric Acid Derivatives... 

In [2+2] photocycloadditions of a,(3-unsaturated ketals derived from C2-symmetric 1,2-diols tartaric acid derivatives (58) proved to be efficient to yield the cycloadducts in up... 

Diethyl tartrate (compared to various tartaric acid derivatives) still remains the best ligand for the enantioselective oxidation of sulfides, as exemplified by the oxidation of methyl p-tolyl sulfide [49]. Yamamoto et al found that DET can be replaced by diols (30) or (31) in the Kagan reagent, giving sulfoxides of opposite... 

The chiral diol 17 derived from tartaric acid is exploited in the titanium-catalyzed asymmetric pinacol coupling in the presence of Zn and MesSiCl to give the corresponding diol in 11-71 ee % [44], The chiral salen ligands 18-20 are used in the titanium-catalyzed enantioselective coupling reaction, which achieves the higher selectivity [45-47]. The chromium complex with TBOxH (21) efficiently catalyzes the asymmetric coupling reaction of both aromatic and aliphatic aldehydes [48]. 

The Lewis acid catalyst 53 is now referred to as the Narasaka catalyst. This catalyst can be generated in situ from the reaction of dichlorodiisopropoxy-titanium and a diol chiral ligand derived from tartaric acid. This compound can also catalyze [2+2] cycloaddition reactions with high enantioselectivity. For example, as depicted in Scheme 5-20, in the reaction of alkenes bearing al-kylthio groups (ketene dithioacetals, alkenyl sulfides, and alkynyl sulfides) with electron-deficient olefins, the corresponding cyclobutane or methylenecyclobu-tene derivatives can be obtained in high enantiomeric excess.18... 

Bidentate chiral auxiliaries have since been examined. While camphane-2,3-diol and (5-binaphthol gave disappointing results, tartrate-derived (TADDOL) ligands were found to be very promising as chiral inductors [44]. Particularly interesting results were obtained by using complex 21, readily available from natural (P,J )-(+)-tartaric acid (Scheme 13.21). 

Chiral titanium catalyst for asymmetric Diels-Alder reactions. A Japanese group2 recently reported that a chiral titanium reagent (1), prepared in situ from TiCl2(0-f-Pr)2 and the chiral diol 2, derived from L-tartaric acid, in combination... 

Due to the complexity of conformational equilibria, the application of the dibenzoate chirality rule to determination of the absolute configuration of acyclic diols and polyols requires cautious evaluation of the CD data. For example, (0,0)-dibenzoyl derivatives of diesters and N.N.N ,AT-tetraalkyldiamides of (/t,f )-tartaric acid give exciton Cotton effects of opposite sign due to the preference of diesters for a planar and tetraalkyldiamides for a gauche conformation of the carbon chain176. 

Osmium tetroxide oxidation of (- )-( )-cyclooctene (6) afforded the ( + )-diol 7 whose absolute configuration was related to that of (+ )-tartaric acid (9) via the (+)-dimethoxy derivative 8. The (R)-configuration assigned by this correlation has been confirmed by a number of direct or indirect approaches. 

Hydroxy-1,2-dicarboxylic acids, such as n- and L-a-hydroxysuccinic acid53 and D-tartaric acid.120 on treatment with sulfur tetrafluoride give complex mixtures of fluoroalkanes, fluoro-alkenes, fluoroalkyl fluorosulfites and cyclic five-membered ethers, derivatives of 2.2,5.5-tet-rafluorotetrahydrofuran. In the case of D-tartaric acid the cyclic ethers are predominant components (64%) of the reaction mixture.120 Linear and cyclic mono- and disulfites formed in these reactions give, after hydrolysis, the corresponding linear and cyclic polyfluoro alcohols and diols in high yield.53120... 

Lewis acid-promoted asymmetric addition of dialkylzincs to aldehydes is also an acceptable procedure for the preparation of chiral secondary alcohol. Various chiral titanium complexes are highly enantioselective catalysts [4]. C2-Symmet-ric disulfonamide, chiral diol (TADDOL) derived from tartaric acid, and chiral thiophosphoramidate are efficient chiral ligands. C2-Symmetric chiral diol 10, readily prepared from 1-indene by Brown s asymmetric hydroboration, is also a good chiral source (Scheme 2) [17], Even a simple a-hydroxycarboxylic acid 11 can achieve a good enantioselectivity [18]. 

A related approach has recently been reported by Belokon and Kagan et al. These workers used chiral TADDOL-type diols, derived from tartaric acid and 2-amino-2 -hydroxy-1,1 -binaphthyl (NOBIN), as catalysts to obtain yields of up to 95% and enantioselectivity up to 93% ee [59-61], The catalytically active species seem to be the sodium salts of the diols. 

Asymmetric [2 + 2] cycloaddition.6 The chiral titanium reagent 4, prepared from TiCl2(0-i-Pr)2 and the chiral diol 1, derived from L-tartaric acid and known to effect asymmetric Diels-Alder reactions (14, 232-233), can also promote asymmetric [2 + 2]cycloadditionof l,l-bis(methylthio)ethylene to a,P-unsaturated N-acylox-azolidinones. 

A -Pyrroline-A xides (nitrones) derived finm tartaric acids feature in several syntheses of 132 and ent- 32. The first of two routes by Brandi and co-workers commenced with a dipolar cycloaddition between the nitrone 142 (R = tert-butyldiphenylsilyl, or TBDPS) and methylenecyclopropane (143), which afforded a mixture of spirocyclopropylisoxazolidine 144 and its bridgehead epimer (10 1) (Scheme 20, top line) (5i). When heated in xylene, 144 rearranged cleanly to enaminone 145 and the indolizidinone 146, the latter undergoing ready conversion via the tosylhydrazone into the target diol, ( + )-132. A subsequent synthesis with... 

Catalysts prepared from polymer-bound 1,2- and 1,4-diols derived from tartaric acid... 

Seebach et al. have comprehensively examined the use of a chiral diol (TAD-DOL) derived from tartaric acid as a chiral ligand [22]. The titanium-TADDOL system also catalyzes the asymmetric addition of diethylzinc to various aldehydes (Scheme 8) [23,24]. This system is applicable to the alkylation of various... 

Narasaka reported that, although the reactions proceeded in a stoichiometric manner, the mixture of TiCl2(Oi-Pr)2 with chiral diol (9a, see Fig. 1) derived from tartaric acid promoted the addition of TMSCN to aromatic aldehydes in the presence of 4 A molecular sieves to yield the corresponding cyanohydrins with an ee of up to 96% [40]. 

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