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SYNLETT0 9 3 6 - 5 2 1 4 1 4 3 7 - 2 0 9 6© Georg Thieme Verlag Stuttgart · New York2015, 26, 416–417spotlight

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(R)-TRIP and (S)-TRIP – Very Recent ApplicationsJosé Tiago Menezes Correia

Instituto de Química, Universidade Estadual de Campinas, UNICAMP, C.P. 6154, CEP 13083-970, Campinas, São Paulo, Brasiljose.correia@iqm.unicamp.br

Published online: 23.01.2015DOI: 10.1055/s-0034-1379876; Art ID: St-2014-v0505-v

José Tiago Menezes Correia was born in Brazil in1986. He received his B.Sc. in chemistry fromthe Federal University of Bahia – UFBA (Bahia,Brasil) in 2010 and his M.Sc. in sciences from theState University of Campinas – UNICAMP (SãoPaulo, Brazil). He is currently a PhD candidateunder the supervision of Prof. Dr. FernandoCoelho also at UNICAMP. His research focuseson the development of organocatalysed strate-gies to access indolizidinic and quinolizidiniccores, starting from Morita–Baylis–Hillman ad-ducts.

Introduction i-Pr i-Pri-Pr1)

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(R)- and (S)-3,3′-bis(2,4,6-triisopropylphenyl)-1,1′-binaphthyl-2,2′-diylhydrogenphosphates, also known as(R)-TRIP and (S)-TRIP are chiral phosphoric acids (CPA’s) de-rived from BINOL. They are available from commercialsources, and they can be prepared through a three-step se-quence that starts with a Kumada coupling between com-pound 1 and two equivalents of 2,4,6-(triisoprop-oxy)phenylmagnesiumchloride. This reaction is followed bya deprotection and a high-yielding phosphorylation step(Scheme 1a).1

Since their first application in enantioselective organo-catalytic hydrogenations by the List Group, in 2005,2 thesecatalysts have been applied in numerous enantioselectivetransformations, including strategies involving cooperativecatalysis.3

Scheme 1 General synthetic sequence for the preparation of (R)- and (S)-TRIP

Table 1 Use of (R)-TRIP and (S)-TRIP – Very Recent Applications

OMe

Br

OMe

Br

OH

OH

i-Pr

i-Pr

i-Pr i-Pr

O

OP

O

OH

i-Pr

i-Pr

i-Pr

i-Pr

i-Pri-Pr

i-Pr i-Pr

BrMg

Ni(PPh3)2Cl2 (10 mol%)

Et2O, 6 h, reflux

2) BBr3, CH2Cl2, 24 h, r.t.45% (2 steps)

POCl3, Pyr,14 h, reflux,

H2O, 3 h, refluxCH2Cl2-HCl99%

1

(A) Early in 2013, List and co-workers reported an asymmetric pro-tonation of silyl ketene imines (SKI’s) catalyzed by (S)-TRIP or STRIP (a spiroderivative of TRIP).4 During the catalyst screening both of these showed high efficiency. This transformation has no prece-dents in literature and showed to be a mild and straightforward strategy to access α-branched nitriles with high enantiopurity.

(B) Faber, Orthaber and co-workers reported an asymmetric allyla-tion reaction between a zinc(II)-allylbutyrolactone species and (het-ero)aromatic aldehydes using TRIP as catalyst.5 DFT studies showed that a complex ion-pair involving TRIP, Zn2+ and substrates is formed prior to enantioenriched β-substituted α-methylenebutyrolactone formation. Although high enantioselectivities had been reached, a two-step total synthesis of natural product (S)-(–)-hydroxymataire-sinol was also performed in order to demonstrate the applicability of the methodology.

R2

R1

N

TBS

R2 CN

R1(S)-TRIP (5 mol%) or STRIP (2.5 mol%)

MeOH (1.2 equiv)–78 °C, 12 h

R1 = Alk

R2 = Ar, adamantyl

up to 97% yield er up to 98:2

O

HO

Br O

+

(S)-TRIP (10 mol%)Zn (6 equiv), NH4Cl (8 equiv)

PhMe–(i-Pr)2O 4:1, 4 °C, 16 h

OH

O

R OR

OH

O

O

MeO

BnO2 steps

OH

O

O

MeO

HO

OH

(S)-(–)-hydroxymatairesinol (46% overall yield)

up to 91% yield up to 99% ee<1:>99 (syn/anti)

using (R)-TRIPMeO

R = Ar, t-Bu, OMe, OBn or halogen

© Georg Thieme Verlag Stuttgart · New York — Synlett 2015, 26, 416–417

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References

(1) Klussmann, M.; Ratjen, L.; Hoffmann, S.; Wakchaure, V.;Goddard, R.; List, B. Synlett 2010, 2189.

(2) Hoffmann, S.; Seayad, A. M.; List, B. Angew. Chem. Int. Ed. 2005,44, 7424.

(3) (a) Mahlau, M.; List, B. Angew. Chem. Int. Ed. 2013, 52, 518.(b) Ávila, E. P.; Amarante, G. W. ChemCatChem 2012, 4, 1713.(c) Rueping, M.; Koenigs, R. M.; Atodiresei, I. Chem. Eur. J. 2010,16, 9350.

(4) Guin, J.; Varseev, G.; List, B. J. Am. Chem. Soc. 2013, 135, 2100.(5) Fuchs, M.; Schober, M.; Orthaber, A.; Faber, K. Adv. Synth. Catal.

2013, 355, 2499.(6) Yu, S.-Y.; Zhang, H.; Gao, Y.; Mo, L.; Wang, S.; Yao, Z.-J. J. Am.

Chem. Soc. 2013, 135, 11402.

(7) Zhang, K.-F.; Nie, J.; Guo, R.; Zheng, Y.; Ma, J.-A. Adv. Synth. Catal.2013, 355, 3497.

(8) (a) Zhang, G. W.; Wang, L.; Nie, J.; Ma, J.-A. Adv. Synth. Catal.2008, 350, 1457. (b) Husmann, R.; Sugiono, E.; Mersmann, S.;Raabe, G.; Rueping, M.; Bolm, C. Org. Lett. 2011, 13, 1044.

(9) (a) Qabaja, G.; Wilent, J. E.; Benavides, A. R.; Bullard, G. E.;Petersen, K. S. Org. Lett. 2013, 15, 1266. (b) Wilent, J.; Petersen,K. S. J. Org. Chem. 2014, 79, 2303.

(10) (a) Cai, X.-F.; Guo, R.-N.; Feng, G.-S.; Wu, B.; Zhou, Y.-G. Org.Lett. 2014, 16, 2680. (b) Guo, R.-N.; Chen, Z.-P.; Cai, X.-F.; Zhou,Y.-G. Synthesis 2014, 46, 2751.

(11) Monaco, M. R.; Poladura, B.; de Los Bernardos, M. D.; Leutzsch,M.; Goddard, R.; List, B. Angew. Chem. Int. Ed. 2014, 53, 7063.

(C) In order to expand the applicability of isochromenyliums in en-antioselective transformations, an asymmetric [4+2] annulation be-tween 2-hydroxystyrenes and isochromenyliums prepared in situ from 2-alkynylbenzaldehyes or 1-(2-alkynylphenyl)ketones was de-veloped by Yao and co-workers.6 Among the catalytic conditions in-vestigated, the combination of Pd(OAc)2 with (S)-TRIP gave the best results. This cooperative catalytic system showed to be applicable for a broad spectrum of substrates. Good to excellent enantioselec-tivities were achieved.

(D) Still in 2013, an asymmetric synthesis of cyclic trifluoromethyl-dihydroquinazolines via a TRIP-catalyzed aza-Friedel–Crafts reac-tion between indoles and cyclic N-acylketimines was developed by Ma and co-workers.7 This work was based on a previous report in which aryl-imines generated in situ from hemi-acetals were used as electrophiles.8a In 2011, Bolm and co-workers had also reported an-other example using trifluoropyruvate derived N-Boc-imines as electrophiles.8b

(E) Recently, the desymmetrization of pro-chiral diesters by an in-tramolecular transesterification catalyzed by TRIP was disclosed and had its scope explored by Petersen and co-workers.9 The pro-cess showed to be scalable and robust, leading to the preparation of several enantioenriched lactones with all-carbon chiral quaternary centers, which showed to be useful small building blocks.

(F) Organocatalysed transfer hydrogenation of heteroaromatic com-pounds has been widely investigated over the last years. Recently, Zhou and co-workers reported the use of TRIP on the asymmetric hydrogenation of 2-aryl-quinolone-3-amines and 3-(trifluorometh-yl)quinolones with up to 99% and 98% ee, respectively.10a,b

(G) Taking advantage of a highly favoured heterodimerization of car-boxylic acids with TRIP, List and co-workers investigated the de-symmetrization of meso-aziridines and the kinetic resolution of terminal aziridines using this catalyst.11 The catalytic system proved useful for the conversion of cyclic and acyclic aziridines into O-pro-tected amino alcohols with high yields and enantioselectivities. This was the first report of a CPA’s catalyzed reaction using carboxylic ac-ids as nucleophiles instead of only as additives, which has opened new perspectives in the field.

R2

O

R3

R1R7

R5R6

R4R1

O

R7

R5

R3

R6

R2O

R4

Pd(OAc)2 (2.5 mol%)(S)-TRIP (3.75 mol%)

CH2Cl2 (0.1 M), r.t., N2

R1 = H, OMe, or di-OMe

R2 = Ar, heteroaryl and Alk

R3 = H, Alk and

electron-rich aryl

R4 = H, EWG and EDG

R5,R6 and R7

= H, Alk(40 examples)up to 92% yieldup to > 99.5% ee

OH

+

NH

N

N

CF3

O

PMBN

NH

F3C

O

PMB

HN

(S)-TRIP (5 mol%)+DCE, –35 °C

R1

R2

up to 98% yieldup to 99% ee

R1 = Alk, halogen, OMe, CN and CO2Me

R2 = Alk, halogen, OMe and CF3

O

O O

O

O O

OR

OH

Rn n

(S)-TRIP (5 mol%)

CH2Cl2

up to 97% yield up to 98% ee

n = 1, 2R = Alk, Bu, allyl

N

R2

Aryl NH

R2

Ar(S)-TRIP (5 mol%)

1,4-dioxane–CH2Cl2 (2:1) or CH2Cl2

(2.4 equiv)

R3OC

NH

COR3

Hanztsch Ester (HE)

R2 = NTs; R3 = CO2Me up to 99% yield up to 99% ee

R1

R1 = H or F

R1

R2 = CF3; R3 = COMe up to 96% yield up to 98% ee

HE

N

COAr

R1 R1

(S)-TRIP (8 mol%)R2OH (7 equiv)

CHCl3, r.t. R1

OR2

R1

ArOCNH

N

COAr

R1

(S)-TRIP (8 mol%)BzOH (7 equiv)

CH2Cl2, –30 °C

BzO

R1

NHCOAr

R1 = Ph, alkyl or cycloalkylR2 = Bz or Acyield up to 99% yield er up to > 99.5:0.5

yield up to 51% + 44% (overall 95%)er up to 96:4 / 98.5:1.5

N

COAr

R1

+

rac(S)

(S)R1 = alkyl or alkylphenyl

© Georg Thieme Verlag Stuttgart · New York — Synlett 2015, 26, 416–417