Nickel-Catalyzed Ring-Opening C-O Functionalization of peri-Xanthenoxanthenes for 8-Substituted Binaphthol Synthesis

Xanthenoxanthenes for 8 ‑Substituted Binaphthol Synthesis

Letter

Nickel-Catalyzed Ring-Opening C−O Functionalization of peri-

Naoki Matsuyama, Naoto Minamino, Toyoshi Shimada, and Toshiyuki Kamei*

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sı Supporting Information

ABSTRACT: Herein, we disclose the Ni-catalyzed ring-opening C−O functionaliza-

tion of peri-xanthenoxanthenes using Grignard reagents that forms 8-monofunction-

alized binaphthols. 1,2-Bis(dicyclohexylphosphino)ethane was the best ligand for

alkylations and ICy for arylation. After mechanistic investigations, we assumed that the

reaction proceeds via C−O reduction and subsequent C−O functionalization. To

verify the mechanism, the intermediate after reduction was isolated. Moreover, the

asymmetric addition, using 8-octylbinaphthol after optical resolution, was studied.

inaphthyl derivatives are widely applied as chiral ligands

and catalysts in many asymmetric transformations.

To prove this hypothesis, we applied the Ni-catalyzed C−O

functionalization, which experienced considerable attention in

this past decade. There have been a few reports on C−O bond

Preferred synthetic strategies for these reagents are modiﬁca-

tions of binaphthol (1,1′-bi-2-naphthol) using electrophilic

activation of diaryl ethers. Martin reported the C−O silylation

10a

of dibenzofuran with silylborane, and Yorimitsu and Osuka

substitutions at 6,6′-positions and directed metalations at 3,3′-

disclosed the C−O arylation of dibenzofuran with ArMgBr.

positions. Although homocoupling reactions of 2-naphthol

Tobisu and Chatani developed the C−O bond alkylation of

derivatives are also available for the synthesis of binaphthol with

10c

diaryl ethers and dibenzofuran with Grignard reagents.

substituents in other positions, the synthesis of 8,8′-function-

We started our investigation to achieve the Ni-catalyzed ring-

opening reaction of PXX 1a employing Tobisu’s reaction

conditions (Table 1). Surprisingly, the reaction of 1a with

alized binaphthols has not been fully developed because of the

steric hindrance of the 8-position of binaphthol.

In our laboratory, we applied Cu-catalyzed ring-closing

reactions of binaphthol to produce peri-xanthenoxanthene

PXX) derivatives (Scheme 1a), which are used as p-type

Ni(cod) (15 mol %), 1,2-bis(dicyclohexylphosphino)ethane

(

dcype) (15 mol %), and n-octylmagnesium iodide (2a, 6 equiv)

(

in toluene for 40 h gave 8-n-octylbinaphthol (3aa) in 71% yield,

accompanied by small amounts of binaphthol 4 (∼9%, Table 1,

transistors for rollable displays by Kobayashi (Sony Corpo-

ration). We think the reductive ring-opening reaction of PXX

to introduce substituents could result in a novel synthetic

strategy for binaphthol derivatives (Scheme 1b).

entry 1), not 8,8′-di(n-octyl)binaphthol. No reaction occurred

with the addition of other bidentate cyclohexylphosphine

ligands, such as 1,3-bis(dicyclohexylphosphino)propane

(

dcypp), 1,1′-bis(dicyclohexylphosphino)ferrocene (dcypf),

Scheme 1. Ring-Closing and Ring-Opening Strategy to

Functionalize Binaphthols

bipyridine, monodentate, and carbene ligands (entries 2−8).

The reaction of 1a with PhMgBr 2A, adding Ni(cod) and

dcype, was unsuccessful, with no recovery of starting materials

(

Table 1, entry 1). After optimization of the ligands, addition of

carbene ligand ICy eﬀectively produced 8-phenylbinaphthol

aA in 58% yield (entry 6). No reactions occurred with 2A

using other ligands listed in Table 1 (entries 2−5, 7, and 8).

Alternative ligands, nickel precursors, Grignard reagents, and

temperature variations were also studied (see Tables S1 −S4).

Received: March 27, 2021

XXXX American Chemical Society

Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters

Letter

Table 1. Ligand Optimizations of Ni-Catalyzed Ring Opening

of PXX

Scheme 3. Ni-Catalyzed Arylative Ring Opening of PXX

entry

ligand (y mol %)

3aa (%)

3aA (%)

dcype (15)

dcypp (15)

dcypf (15)

trace

dppe (15)

PCy (30)

Icy·HCl (30)

I(1-Ad)·HBF (30)

bipyridine (15)

H NMR yield. Isolated yield. Binaphthol (R = H) 4 was obtained

(

9%). 1,1′-Bis(dicyclohexylphosphino)ferrocene.

We applied this reaction further using other Grignard reagents

Scheme 2). Butylmagnesium iodide produced 3ab in high

(

Scheme 2. Ni-Catalyzed Alkylative Ring Opening of PXX

120 °C.

bromide yielded 84% 3aE. The presence of electron-donating

groups in the Grignard reagent enhanced the reactivity, and 3aF

was also obtained in 84% yield. Electron-withdrawing ﬂuoro

groups reduced the reactivity to give 3aG in 49% yield. When the

substituents on PXX were examined, the reaction with 2,8-di(t-

butyl)PXX and 2,8-di(p-t-butylphenyl)PXX produced the

corresponding products 3bD and 3cD, but the phenyl groups

at the 5- and 11-positions prevented the ring-opening reaction.

To gain further insight on the mechanism of the trans-

formation, we analyzed the products of the reaction prior to full

conversion (Scheme 4). The alkylation with 2a formed the half-

Scheme 4. Half-Time Reactions to Capture Intermediates

EtMgBr (6 equiv) and MgI (2.2 equiv) were added. ^bⁱPrMgI was

used.

yields. Ethylmagnesium bromide was, together with MgI , the

10c

most suitable reagent to obtain 3ac in low yields (38%).

Addition of n-dodecylmagnesium iodide 2d and isobutylmag-

nesium iodide 2e formed 3ad and 3ae also in low yields. Using

isopropylmagnesium iodide 2f, isomerization to n-propylnickel

occurred to produce 8-n-propylbinaphthol in 48% yield. Probing

the β-H elimination of alkylnickel was included in the later

reaction mechanism study.

ring-opening product 5 as the main product (56% yield), with

3aa in 24% yield. Regarding the arylation, trace amounts of 5

were detected with H NMR in the crude products, and the main

The results using aryl Grignard reagents are shown in Scheme

. The reaction with o-tolylmagnesium bromide produced the

product 3aA was isolated in 48% yield. These results proved that

the reaction proceeds via reductive ring-opening and alkylative/

arylative binaphthol formation.

Next, we investigated the hydrogen source of the reduction.

The β-H elimination of alkylnickel intermediates was observed

corresponding product 3aB in low yields (36%), related to the

steric hindrance of the o-methyl group. Addition of m- and p-

tolylmagnesium bromide successfully formed 3aC and 3aD in

high yields. The reaction of p-tert-butylphenylmagnesium

Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters

Letter

during the reaction with isopropylmagnesium iodide (3f).

Therefore, we subjected Grignard reagents with no hydrogen in

the β-position, such as methylmagnesium iodide and trime-

thylsilylmethylmagnesium iodide, to ring-opening conditions to

Scheme 7. Possible Mechanisms of Ni-Catalyzed Ring

Opening with Alkyl Grignard Reagent

recover the starting materials (Scheme 5).

Scheme 5. Reaction with Grignard Reagent without β-

Hydrides

To identify the hydrogen source, the reaction was quenched

with D O (Scheme 6). The addition of D O to 1a and 2a did not

Scheme 6. Deuterium-Labeled Experiments

complex. Reductive elimination yields half-ring-opening prod-

uct 5 (cycle I). The oxidative addition of Ni to another C−O

bond, followed by transmetalation and reductive elimination,

results in the products shown in cycle II. In the case of aryl

Grignard reagents, 5 is produced similarly to that with alkyl

Grignard reagents, following a cross-coupling sequence to

obtain the corresponding products; however, the hydrogen

source could not be determined.

Finally, to ensure the suitability of the 8-alkyl substituent for

asymmetric reactions, the enantioselective alkylation of carbonyl

compounds with a zinc reagent was used as a model reaction

(

Scheme 8). The enantiomerically pure binaphthol 3aa was

Scheme 8. Enantioselective Alkylation of 1-Naphthaldehydes

result in incorporation of deuterium (D) into 3aa. Adding D O

to the mixture of 1a and 2A also did not produce 3aA with D

atoms included. Furthermore, the reaction of 1a and 2A

performed in toluene-d aﬀorded 3aA without D atoms. The D-

incorporated Grignard reagent (2A-d ) was subjected to the

resolved using camphor sulfonyl ester column chromatography

reaction to result in 0% D at the 8-position. Mechanism of the

reaction with aryl magnesium bromide did not include β-

hydride elimination.

(Scheme S2 ). The reaction of α-naphthaldehyde and diethyl

zinc in the presence of Ti(O Pr) and (R)-3aa produced 1-(α-

naphthyl)-1-propanol 6 in 74% yield and 98% ee. The control

experiment using (R)-binaphthol instead of (R)-3aa yielded the

product in 81% yield and 78% ee (ref 15 reports products

obtained in 94% yield and 85% ee). These results show that the

8-substituted binaphthol can control asymmetric reactions.

In conclusion, we achieved the Ni-catalyzed C−O bond

activation of PXX to aﬀord 8-substituted binaphthol derivatives

in high yields. The reaction proceeds through the reductive half-

ring-opening of PXX. Hydride is derived from β-H elimination

of alkyl nickel intermediates. Cross-coupling with alkylation or

arylation provides the 8-substituted binaphthol derivatives. The

suitability of the products as ligands in asymmetric reactions was

A possible reaction mechanism is shown in Scheme 7. The

oxidative addition of a Ni catalyst into the C−O bond, using the

Grignard reaction, is followed by the transmetalation with

Grignard reagents to produce complex II. Oxidative addition of

Ni(0) species was well examined on Ni-catalyzed reduction of

diphenyl ether. Oxidative addition proceeded via the η -benzene

complex. Ni(0) complex might be slightly sterically accessible

to the benzene structure, including a C −O atom to form the η -

complex. The inhibition of free rotation of the axial bond caused

steric congestion and was strict with the reductive elimination,

and β-H elimination is preferred, forming a nickel hydride

Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters

(4) For example, see: (a) Noji, M.; Nakajima, M.; Koga, K. A New

Letter

examined using (R)-8-n-octylbinaphthol. Studies to determine

the hydrogen source in the case of arylations and apply the 8-

substituted binaphthol in other asymmetric reactions are

ongoing.

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ASSOCIATED CONTENT

sı Supporting Information

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The Supporting Information is available free of charge at

https://pubs.acs.org/doi/10.1021/acs.orglett.1c01053.

Experimental procedures and compound characterization

(PDF)

968, 90, 7134−7135.

AUTHOR INFORMATION

Corresponding Author

(5) 8,8’-Disubstituted binaphthols: (a) Katsuki, N.; Isshiki, S.;

Fukatsu, D.; Okamura, J.; Kuramochi, K.; Kawabata, T.; Tsubaki, K.

Total Synthesis of Dendrochrysanene through a Frame Rearrangement.

J. Org. Chem. 2017 , 82 , 11573 −11584. (b) Podlesny, E. E.; Carroll, P. J.;

Kozlowski, M. C. Selective Oxidation of 8,8 ’-Hydroxylated Binaphthols

to Bis-spironaphthalenones or Binaphtho-para- and Binaphtho-ortho-

quinones. Org. Lett. 2012, 14, 4862−4865. (c) Terrasson, V.; Roy, M.;

■

Toshiyuki Kamei − Department of Chemical Engineering,

National Institute of Technology, Nara College,

Yamatokoriyama, Nara 639-1080, Japan; orcid.org/

000-0001-8435-3767 ; Email: kamei@chem.nara-k.ac.jp

Moutard, S.; Lafontaine, M.-P.; Pepe; Felix, G.; Gingras, M. Benzylic-

̀ ̀

type couplings provide an important asymmetric entry to function-

Authors

alized, non-racemic helicenes. RSC Adv. 2014, 4, 32412−32414.

Naoki Matsuyama − Department of Chemical Engineering,

(

d) Vesely, V.; Stursa, F. 1-Methyl-7-naphthol. Collect. Czech. Chem.

National Institute of Technology, Nara College,

Yamatokoriyama, Nara 639-1080, Japan

Commun. 1933, 5, 170−178.

(6) (a) Kamei, T.; Uryu, M.; Shimada, T. Cu-Catalyzed Aerobic

Naoto Minamino − Department of Chemical Engineering,

National Institute of Technology, Nara College,

Yamatokoriyama, Nara 639-1080, Japan

Oxidative C −H/C −O Cyclization of 2,2 ’-Binaphthols: Practical

Synthesis of PXX Derivatives. Org. Lett. 2017, 19, 2714−2717.

(b) Kamei, T.; Nishino, S.; Yagi, A.; Segawa, Y.; Shimada, T. Ni-

Toyoshi Shimada − Department of Chemical Engineering,

National Institute of Technology, Nara College,

Yamatokoriyama, Nara 639-1080, Japan

Catalyzed α -Selective C −H Borylation of Naphthalene-Baseed

Aromatic Compounds. J. Org. Chem. 2019, 84 , 14354 −14359.

(7) Kobayashi, N.; Sasaki, M.; Nomoto, K. Stable peri -Xanthenox-

anthene Thin-Film Transistors with Efficient Carrier Injection. Chem.

Mater. 2009, 21, 552−556.

Complete contact information is available at:

https://pubs.acs.org/10.1021/acs.orglett.1c01053

(8) For selected reviews, see: (a) Tobisu, M.; Chatani, N. Cross-

Couplings Using Aryl Ethers via C −O Bond Activation Enabled by

Nickel Catalysts. Acc. Chem. Res. 2015 , 48 , 1717 −1726. (b) Li, B.-J.; Yu,

D.-G.; Sun, C.-L.; Shi, Z.-J. Activation of “Inert ” Alkenyl/Aryl C −O

Bond and Its Application in Cross-Coupling Reactions. Chem. - Eur. J.

Notes

The authors declare no competing ﬁnancial interest.

011, 17, 1728−1759. (c) Rosen, B. M.; Quasdorf, K. W.; Wilson, D.

ACKNOWLEDGMENTS

■

A.; Zhang, N.; Resmerita, A.-M.; Garg, N. K.; Percec, V. Nickel-

Catalyzed Cross- Couplings Involving Carbon −Oxygen Bonds. Chem.

Rev. 2011 , 111 , 1346 −1416. (d) Cornella, J.; Zarate, C.; Martin, R.

Metal-catalyzed activation of ethers via C −O bond cleavage: a new

strategy for molecular diversity. Chem. Soc. Rev. 2014 , 43 , 8081 −8097.

We are grateful to Prof. Mamoru Tobisu (Osaka University) for

his helpful advice. This work was supported by Grant-in-Aid for

Young Scientists (B) JP15K17859. We would like to thank

Editage (www.editage.com ) for English language editing.

e) Qiu, Z.; Li, C.-J. Transformations of Less-Activated Phenols and

Phenol Derivatives via C −O bond Cleavage. Chem. Rev. 2020, 120,

0454−10515.

9) Wenkert, E.; Michelotti, E. L.; Swindell, C. S. Nickel-induced

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