Resolution and Novel Reactions of 4-Hydroxy[2.2]paracyclophane

Rozenberg, V. I.; Danilova, Tatyana I.; Сергеева, Е. В.; Воронцов, Е. В.; Starikova, Z. A.; Korlyukov, A. A.; Hopf, Henning

doi:10.1002/1099-0690(20022)2002:3<468::aid-ejoc468>3.0.co;2-3

Cited by 46 publications

(30 citation statements)

References 44 publications

(31 reference statements)

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“…7 Its resolution was realized using naproxen acid chloride instead of the more expensive camphanoyl chloride. 8 The two diastereoisomers were purified three times by crystallizations. Esters (S p ,S)-4 and (R p ,S)-4 were reduced with LiAlH 4 to produce (S)-3 and (R)-3 in 90% yields and in >99% ee, respectively.…”

Section: Resultsmentioning

confidence: 65%

Synthesis of planar chiral [2.2]paracyclophane monophosphine ligands and their application in the umpolung allylation of aldehydes

Zhang

Dai

Hou

2007

Tetrahedron: Asymmetry

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Section: Resultsmentioning

confidence: 65%

Synthesis of planar chiral [2.2]paracyclophane monophosphine ligands and their application in the umpolung allylation of aldehydes

Zhang

Dai

Hou

2007

Tetrahedron: Asymmetry

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“…16 In the present study, we improved the procedure for the isolation of enantiomers of phenol 8 from diastereo merically pure esters by using the hydrolysis with KOH in an aqueous methanolic mixture (see Scheme 2) instead of the reduction of esters 10 with a large excess of LiAlH 4 in anhydrous THF (the yield of 8 was 93%). 15 In this case, the refluxing of individual diastereomers of 10 in a Soxhlet apparatus during a long period of time (6-12 h) is not required; the hydrolysis is completed in 2 h at room tem perature and gives enantiomers of phenol 8 in almost quantitative yield.…”

Section: Resultsmentioning

confidence: 99%

Planar chiral hydroxy derivatives of [2.2]paracyclophane as auxiliaries for asymmetric allylboration

et al. 2007

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Allylboronic esters with various structures were synthesized for the first time based on [2.2]paracyclophane derivatives containing one or two hydroxy groups. It was demonstrated that these esters can be used as chiral inductors in the asymmetric allylboration of benzalde hyde. The highest enantiomeric excess of 1 phenylbut 3 en 1 ol (60%) was achieved in the reactions with acyclic bis O,O´ (paracyclophanyl) allylboronates based on (S) 4 hydroxy and (S) 12 bromo 4 hydroxy[2.2]paracyclophanes. (S) 4 Hydroxy[2.2]paracyclophane was studied by X ray diffraction.The allylboration of aldehydes is one of the most widely used approaches to the stereoselective C-C bond forma tion. 1-4 Generally, enantiomerically pure compounds (diols, diamines, sulfamides, and amino alcohols) pos sessing central 4 or (more rarely) axial chirality 5 are used for the design of reagents for the asymmetric allylboration.Earlier, 6,7 we have demonstrated for the first time that planar chiral [2.2]paracyclophane derivatives can be used in this reaction. For example, diastereomerically pure diallylborinate 2 was synthesized starting from 4 acetyl[2.2]paracyclophane (1) 8,9 (Scheme 1).Compound 2 was used in the allylboration of 4 for myl[2.2]paracyclophane (4) (de of rel (R p ,R) 4 (1 hydr oxybut 3 enyl)[2.2]paracyclophane (5) 50%) and benz aldehyde (6) (ee of 1 phenylbut 3 en 1 ol (7) was 18%). Homoallylic alcohol 3 produced in the reaction is a re cyclable auxiliary because it again gives ester 2 in the reaction with triallylborane (see Scheme 1).In alcohol 3, the hydroxy group is two bonds from the paracyclophane moiety. In the present study, we investi gated the influence of the distance between the functional group and the paracyclophane moiety on the stereochemi cal result of asymmetric allylboration of benzaldehyde. For this purpose, we examined for the first time the possi bility of designing reagents for the asymmetric allyl boration based on chiral phenols, viz., (S) 4 hydr oxy[2.2]paracyclophane (8) and (S) 12 bromo 4 hydr oxy[2.2]paracyclophane (9), in which the hydroxy group is directly fixed in the aromatic ring of [2.2]paracyclo phane.An important feature, which distinguishes phenols 8 and 9 from alcohol 3 containing two stereogenic centers, is that they contain only one (planar) chirality center, which eliminates the question about the possible coop erative effect of the planar and central chirality in the asymmetric process. Results and DiscussionSynthesis of starting phenols 8 and 9. Racemic phenol 8 was synthesized according to a known procedure. 10 To synthesize its enantiomers, we have developed 11-14 a pro cedure for the resolution of rac 8 into enantiomers through esters with (1S) (-) camphanic acid 10 (Scheme 2). 15, 16 Diastereomeric esters 10 were separated by fractional crystallization 15 followed by the preparative separation of the mother liquor by silica gel column chromatography. 16 In the present study, we improved the procedure for the isolation of enantiomers of phenol 8 from diastereo merically pure esters by us...

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“…In an analogous fashion, (R p )-4,12-dibromo[2.2]paracyclophane (4) was first converted into methoxyparacyclophane (10) via bromine-lithium exchange with n-BuLi, trapping of the anion with B(OMe) 3 , subsequent oxidation giving 9, and alkylation with MeI. 23 Benzyl bromide 12 was then derived from 10 by reaction with n-BuLi and paraformaldehyde followed by PBr 3 bromination. Benzyl bromides 7 and 12 as key intermediates Interestingly, all changes had only a minor effect on the enantioselectivity of the process.…”

Section: Methodsmentioning

confidence: 99%

Planar Chiral Imidazolium Salts in the Asymmetric Rhodium-Catalyzed 1,2-Addition of Arylboronic Acids to Aldehydes

Focken¹,

Rudolph²,

Bolm³

2005

Synthesis

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Planar chiral imidazolium salts 8 and 13 were used as precursors for N-heterocyclic carbene ligands, which were applied in rhodium-catalyzed additions of arylboronic acids to aromatic aldehydes. With pseudo-ortho-disubstituted [2.2]paracyclophane (S,R p )-8b bearing a phosphinoyl substituent at the paracyclophane backbone, 38% ee has been achieved in this rather unexplored reaction.Chiral diarylmethanols 3 are structural core units in a number of pharmacologically active compounds. 1 They are accessible by asymmetric reduction of prochiral ketones 2 and enantioselective aryl transfer reactions to aldehydes. [3][4][5] Recently, we developed various approaches involving arylzinc reagents to obtain diarylmethanols in high yields and excellent enantioselectivities. 4 By applying mixtures of arylboronic acids and diethylzinc the product range was significantly broadened. 5All these aryl transfer methods make use of air-sensitive organometallic reagents, which limit their large-scale application. A solution could be the application of arylboronic acids (without any additive), which are easy to handle and are commercially available or straightforward to prepare. Rhodium-catalyzed additions of arylboronic acids to aromatic aldehydes 1 have been reported by Miyaura in 1998 (Scheme 1). 6-8 The corresponding diarylmethanols 3 were obtained in good to superb yields, and with MeO-MOP 9 as chiral ligand a product with 41% ee was formed in the asymmetric addition of phenylboronic acid to 1-naphthaldehyde. 6a A subsequent attempt by Frost to improve this result by using sparteine or bisoxazolines as ligands remained unsuccessful (<10% ee). 10 Scheme 1In 2001 Fürstner reported aryl transfer reactions from arylboronic acids to aldehydes catalyzed by a rhodium complex bearing an in situ formed N-heterocyclic carbene (NHC). 11 With a 1:1 combination of RhCl 3 ·3H 2 O or [Rh(OAc) 2 ] 2 and a sterically hindered imidazolium salt (1-3 mol%), using NaOMe as base in aqueous DME at 80°C, good to excellent yields of 3 were achieved.Complexes with NHC ligands have recently attracted significant attention and much progress has been made with regard to their synthesis and application in homogenous metal catalysis. 12 One of the most prominent examples is the use of NHC ruthenium complexes in olefin metathesis, where they exhibit much superior catalytic properties than their analogs bearing phosphine ligands. 13 Chiral NHCs have been used first by Herrmann and Enders, 14 and since then they found numerous applications in asymmetric metal catalysis. 15 In 2002 we described the first planar chiral NHC and the attempt to apply this ferrocenebased ligand in rhodium-catalyzed hydrosilylations. 16 Soon after we prepared iridium complexes derived from planar-chiral imidazolium salts with pseudo-ortho-disubstituted [2.2]paracyclophane backbones. 17,18 Their use in asymmetric hydrogenations led to products with up to 89% ee.We wondered, if [2.2]paracyclophane-based NHCs could also be applied as chiral ligands in rhodium-catalyzed aryl transfer reaction...

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Resolution and Novel Reactions of 4-Hydroxy[2.2]paracyclophane

Cited by 46 publications

References 44 publications

Synthesis of planar chiral [2.2]paracyclophane monophosphine ligands and their application in the umpolung allylation of aldehydes

Synthesis of planar chiral [2.2]paracyclophane monophosphine ligands and their application in the umpolung allylation of aldehydes

Planar chiral hydroxy derivatives of [2.2]paracyclophane as auxiliaries for asymmetric allylboration

Planar Chiral Imidazolium Salts in the Asymmetric Rhodium-Catalyzed 1,2-Addition of Arylboronic Acids to Aldehydes

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