Synthesis of Di- and Triarylmethanes through Palladium-Catalyzed Reductive Coupling of N -Tosylhydrazones and Aryl Bromides

SYNTHESIS

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2016, 48, A–N

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A

Y. Xia et al.

Paper

Synthesis

Synthesis of Di- and Triarylmethanes through Palladium-Catalyzed

Reductive Coupling of N-Tosylhydrazones and Aryl Bromides

Yamu Xia^a,b

Fangdong Hu^b

Ying Xia^b

NNHTs

Ar²

cat. Pd

Ar²Br

+

Ar¹

R

Ar¹

[H], base

Zhenxing Liu^b

Fei Ye^b

R = H, Ar³

62 examples

30–95%

Yan Zhang^b

Jianbo Wang*^b

^aCollege of Chemical Engineering, Qingdao University of Science

Technology, Qingdao 266042, P. R. of China

^bKey Laboratory of Bioorganic Chemistry and Molecular Engineering

of Ministry of Education, College of Chemistry, Peking University,

Beijing 100871, P. R. of China

wangjb@pku.edu.cn

Received: 27.07.2016

Accepted after revision: 14.09.2016

Published online: 13.10.2016

Negishi cross-coupling reaction with arylzinc reagents for

the synthesis of a series of structurally diverse diarylmeth-

anes.^5d

DOI: 10.1055/s-0036-1588893; Art ID: ss-2016-h0531-op

Among the transition-metal-catalyzed cross-coupling

reactions, palladium-catalyzed reactions have been proven

powerful for the synthesis of di- and triarylmethanes.⁶For

the synthesis of diarylmethanes, Sarkar developed an

Hiyama coupling of benzylic halides with aryltrialkoxysila-

nes using palladium catalysts.^6bMcLaughlin reported a

Suzuki–Miyaura cross-coupling reaction between benzylic

phosphates and arylboronic acids to access diarylmeth-

anes.^6eIn contrast, the methods for the synthesis of triaryl-

methanes are less developed.⁷Walsh provided an approach

to triarylmethanes by the coupling of diarylmethanes and

aryl bromides by transforming the benzylic C–H bonds into

the C–C bonds.^7cKuwano and co-workers presented a cou-

pling between diarylmethyl carbonates and arylboronic

acids.^7fMore recently, Hirano and Miura reported a Pd-

catalyzed coupling of oxazoles with diarylmethyl carbon-

ates or pivalates to afford triarylmethanes in good yields.^7a

Although many efforts have been devoted to this area, it is

still highly desirable to develop novel and efficient coupling

reactions for the synthesis of di- and triarylmethanes.

N-Tosylhydrazones are commonly used substrates in or-

ganic synthesis and they can be readily accessed by conden-

sation of carbonyl compounds with N-tosylhydrazide. Re-

cently, N-tosylhydrazones have been proven as a new type

of cross-coupling partners in Pd-catalyzed reactions.⁸In

these reactions, N-tosylhydrazones are first converted to

non-stabilized diazo compounds in situ with base through

Bamfod–Stevens reaction.⁹Then dinitrogen extrusion oc-

curs to form Pd carbene intermediates, which undergo mi-

gratory insertion leading to the formation of C−C single

bond.^8,10Recently, Pd-catalyzed cross-coupling reactions of

N-tosylhydrazones with benzyl halides, terminal alkynes,

and boronic acids have been well established.¹¹In these re-

Abstract A palladium-catalyzed reductive coupling between N-tosyl-

hydrazones and aryl bromides has been developed. The reaction pro-

vides an efficient method for the synthesis of diarylmethanes and tri-

arylmethanes via the formation of C(sp²)–C(sp³) single bonds. This new

methodology for the synthesis of diarylmethanes and triarylmethanes

is featured by the ready availability of the starting materials, mild reac-

tion conditions, and the tolerance of wide range of functional groups.

The reaction follows a pathway including palladium carbene formation,

migratory insertion, and reduction of the alkylpalladium(II) intermedi-

ate.

Key words N-tosylhydrazone, cross-coupling, carbene, palladium, di-

arylmethane, triarylmethane

Di- and triarylmethanes are important motifs, which

widely exist in natural products, pharmaceutically related

compounds, and supramolecular structures.^1,2In view of

their importance in various fields, the development of syn-

thetic methods that can rapidly access di- and triarylmeth-

anes from readily available starting materials has attracted

significant attention.³The traditional methods to access di-

and triarylmethanes are Friedel–Crafts alkylations and

their variants, which form a C–C bond by introducing an al-

kyl group into an aromatic ring.⁴These methods, although

widely used, are generally found difficult to be applied for

the synthesis of di- and triarylmethanes bearing electron-

withdrawing groups or meta-substituents. Recently, the

method based on transition-metal-catalyzed cross-cou-

pling reactions has emerged as efficient and practical tools

for the synthesis of di- and triarylmethanes.⁵For example,

Watson developed a nickel-catalyzed cross coupling of ben-

zylic ammonium triflates with arylboronic acids to give di-

arylmethanes.^5cBedford reported an iron(I)-catalyzed

B

Y. Xia et al.

Paper

Synthesis

(A)

β-hydride

migratory

insertion

Ar

R²

NNHTs

LnPd

R¹

Ar

LnPd

R¹

Ar

R¹

elimination

ArPdLn

R²

R¹

LnPdH

(B)

This work

Ar²

migratory

insertion

Ar²

NNHTs

R

[H] reduction

LnPd

Ar¹

LnPd

Ar¹

Ar²PdLn

Ar¹

R

Ar¹

R

LnPdH

R = H, Ar³

Scheme 1 Pd-Catalyzed cross-coupling of N-tosylhydrazones

actions, the regeneration of Pd catalyst was achieved via β-

hydrogen elimination of palladium species that are generat-

ed from Pd carbene migratory insertion, leading to the for-

mation of C=C double bond. Thus, the N-tosylhydrazones

can be considered as vinylmetallic reagent equivalents in

these cases (Scheme 1 A). In 2013, we communicated a pal-

ladium-catalyzed reductive cross coupling of N-tosylhydra-

zones, in which the N-tosylhydrazones can be considered as

alkylmetallic reagent precursors. The reaction is a novel

and efficient approach toward triarylmethanes (Scheme 1

Table 1 Condition Optimization for the Pd-Catalyzed Reductive Cross-Coupling Reaction^a

NNHTs

Br

cat., ligand, [H]

H

+

base, solvent, 12 h

Ph

3a

2a

1a

Entry

Cat. (mol%)

Ligand (mol%)

[H]

Base

Solvent

Temp (°C)

Yield (%)^b

1

2

Pd(PPh₃)₄(5)

Pd(OAc)₂(5)

none

HCO₂NH₄

K₂CO₃

DCE

90

80

70

80

trace

<5

Cs₂CO₃

t-BuOLi

Cs₂CO₃

DCE

3

HCO₂NH₄

Et₃SiH

DCE

0

4

DCE

trace

<10

trace

<10

23

5

i-PrOH

DCE

6

P(2-furyl)₃(15)

Xphos (15)

HCO₂NH₄

i-PrOH

DCE

7

DCE

8

PCy₃·HBF₄(15)

PCy₃·HBF₄(20)

DCE

9

toluene

1,4-dioxane

MeCN

toluene

10

11

12^c

13^d

14^d

15^d

16^e

17^f

18^f

i-PrOH

0

i-PrOH

trace

50

i-PrOH

57

i-PrOH

40

i-PrOH

54

i-PrOH

51

i-PrOH

74

i-PrOH

80

^aUnless otherwise noted, the reaction was carried out with 1a (0.30 mmol), 2a (0.30 mmol), [H] (0.3 mmol), and base (2.0 equiv) in solvent (3 mL) for 12 h.

^bYields refer to the isolated products.

^cToluene (2.5 mL), i-PrOH (0.5 mL).

^dToluene (2.7 mL), i-PrOH (0.3 mL).

^eToluene (2.7 mL), i-PrOH (0.3 mL), 1a/2a = 1.5:1.

^fToluene (2.7 mL), i-PrOH (0.3 mL), 1a/2a = 1.2:1.

C

Y. Xia et al.

Paper

Synthesis

B, R = Ar³).¹²As a continuation of our interest in carbene-

coupling reactions, we have further extended the substrate

scope of this reaction and developed an efficient access to-

ward diarylmethanes (Scheme 1 B, R = H). Herein we report

the details of this methodology.

At the outset, we chose benzaldehyde N-tosylhydrazone

1a and 4-bromo-1,1′-biphenyl (2a) as the substrates to op-

timize the reductive coupling reaction (Table 1). Initially, it

was observed that with Cs₂CO₃as the base the expected

coupling product 3a could be isolated, albeit in only low

yield (Table 1, entry 2). With Cs₂CO₃as the base and DCE as

the solvent, the effect of phosphine ligands and reducing

agents were then examined, but the reactions did not gave

satisfactory results (entries 6–8). Next, the effect of solvent

was investigated (entries 9–11), toluene was found to afford

an improved result (entry 9). It was noted that the direct re-

duction of 2a to biphenyl was the major side reaction. Fur-

ther optimization of the reaction conditions revealed that

the reaction yields could be significantly improved by rais-

ing the equivalent of reducing agent i-PrOH (entries 12 and

13). Furthermore, the temperature was found not signifi-

cantly affect the reaction (entries 14 and 15). Finally, the re-

action could be further improved by increasing the loading

of ligand and the substrate ratio of 1a to 2a (entries 16–18).

The optimized reaction conditions are shown in entry 18,

under which the coupling product 3a could be obtained in

80% yield.

With the optimized conditions in hand, the scope of the

reaction we first explored with benzaldehyde N-tosylhy-

drazone and a variety of aryl bromides (Scheme 2). The re-

actions occurred smoothly with electron-donating and

electron-withdrawing substituted aryl bromides to afford

the corresponding diarylmethanes in moderate to good

yields, and that ortho-, para- and meta-substituted sub-

strates could also provide satisfactory results (3a–n). Nota-

bly, the reaction exhibited good tolerance to various func-

tional groups including carbonyl, methoxycarbonyl, and

trimethylsilyl (3h–j). Aryl bromides containing fused ring

gave the coupling products in diminished yields (3o,p). In

Pd(OAc)₂(5 mol%)

PCy₃•HBF₄(20 mol%)

NNHTs

Ar Br

+

Ph

Ar

Ph

H

Cs₂CO₃(2.0 equiv)

ⁱPrOH, toluene

80 °C, 12 h

1a

2a–t

3a–t

3a, X = Ph, 80%

3f, X = CF₃, 67%

3g, X = F, 73%

3h, X = CO₂Me, 61%

3i, X = C(O)Me, 70%

3b, X = ^tBu, 71%

3c, X = H, 66%

3d, X = Me, 63%

Ph

X

3e, X = OMe, 74% 3j, X = SiMe₃, 65%

NNHTs

H

Pd(OAc)₂(5 mol%)

PCy₃•HBF₄(20 mol%)

OMe

Me

OMe

Ph

Ar²Br

Ar¹

4a–j

Ar²

+

Ph

Cs₂CO₃(2.0 equiv)

ⁱPrOH, toluene

80 °C, 12 h

2a,b,e,i

1b–f

3k, 80%

3l, 74%

3m, 60%

Me

Ph

MeO

X

Ph

X

OMe

4d, X = ^tBu, 41%

4e, X = Ph, 48%

4a, X = Ph, 66%

4b, X = ^tBu, 64%

4c, X = F, 52%

Me

3p, 50%

3n, 62%

3o, 58%

O

Ph

X

N

4f, X = ^tBu, 50%

4g, X = OMe, 43%

N

Boc

3q, 75%

3r, 81%

3s, 54%

Ph

MeO₂C

X

Me

^tBu

S

4j, 53%

4h, X = Ph, 38%

4i, X = ^tBu, 43%

3t, 52%

Scheme 2 Substrate scope of aryl bromides for the synthesis of diaryl-

methanes. All reactions were carried out with 1a (0.36 mmol), 2a–t

(0.30 mmol), Pd(OAc)₂(0.015 mmol), PCy₃·HBF₄(0.060 mmol), Cs₂CO₃

(0.60 mmol), and i-PrOH (0.3 mmol) in toluene (2.7 mL) at 80 °C for 12

h. Yields refer to the isolated products by silica gel column chromatog-

raphy.

Scheme 3 Substrate scope of N-tosylhydrazones for the synthesis of

diarylmethanes. All the reactions were carried out with 1b–f (0.36

mmol), 2a,b,e,i (0.30 mmol), Pd(OAc)₂(0.015 mmol), PCy₃·HBF₄

(0.060 mmol), Cs₂CO₃(0.60 mmol), and i-PrOH (0.3 mmol) in toluene

(2.7 mL) at 80 °C for 12 h. Yields refer to the isolated products by silica

gel column chromatography.

D

Y. Xia et al.

Paper

Synthesis

addition, the scope of substrates was extended to hetero-

aromatic bromides and the corresponding products were

obtained in moderate to good yields (3q–t).

As shown in Scheme 6, the reductive coupling reactions

provided the corresponding triarylmethanes in moderate to

excellent yields. The aryl bromides with both electron-rich

and electron-deficient substituents were effective, and that

the substituents on the para- or meta-position could afford

the products in 66–95% yield (6a–m). However, an ortho

substituent gave slightly lower yield (6n). Notably, the aryl

bromides containing fused ring were also suitable sub-

strates for this reaction (6o,p). In addition, the heteroaryl

bromides could be tolerated under the given reaction con-

ditions (6q–t).

Next, the reaction was examined with a series of N-to-

sylhydrazones 1b–f as the substrates to react with aryl bro-

mides 2a, 2b, 2e, and 2i. As shown in Scheme 3, it was ob-

served that the reaction could tolerate a variety of function-

al groups in the N-tosylhydrazones. The substrates bearing

both electron-donating and electron-withdrawing substit-

uents on the aromatic ring could afford the corresponding

products in moderately high yields.

In order to demonstrate the practical application of this

reductive coupling method, the standard reaction was

scaled up and was carried out for gram-scale preparation.

As show in Scheme 4, the reaction gave the desired product

3a in good yield.

Pd(OAc)₂(5 mol%), L (15 mol%)

Ph

HCO₂NH₄(1.2 equiv)

NNHTs + Ar Br

Ar

Cs₂CO₃(2.0 equiv)

MeCO₂NH₄(1.5 equiv)

tert-pentanol, 90 °C, 4 h

2

6a–t

5a

Pd(OAc)₂

Ph

Br

(5 mol%)

Ph

6a, X = ^tBu, 91%

6b, X = H, 81%

6f, X = NHAc, 78%

6g, X = CF₃, 72%

6c, X = Me, 75% 6h, X = F, 66%

NNHTs

PCy₃•HBF₄

(20 mol%)

H

+

X

6d, X = Ph, 80% 6i, X = CO₂Me, 92%

6e, X = OMe, 80% 6j, X = CHO, 83%

Cs₂CO₃

Ph

6k, X = Cl, 76%

6l, X = C(O)Me, 95%

(2.0 equiv)

Ph

ⁱPrOH (0.3 mL)

X

3a, 63% (0.77 g)

1a (1.2 equiv)

2a (5 mmol)

toluene (2.7 mL)

80 °C, 12 h

Me

MeO

Ph

Scheme 4 Gram-scale preparation of 3a

Ph

Me

Furthermore, we proceeded to extend the reductive

cross-coupling method for the synthesis of triarylmethanes.

N-Tosylhydrazone 5a and aryl bromide 2b were employed

as the substrates to optimize the reaction. However, under

the above optimized reaction conditions, the reaction only

afforded a trace amount of the coupling product 6a. Thus, a

series of experiments were carried out to improve the

yields. Finally, it was concluded that under the reaction

conditions described in Scheme 5, the desired coupling

product could be isolated in 91% yield.¹³It should be noted

that this part of the study has been previously published in

a preliminary communication.¹²

6n, 58%

6o, 74%

6m, 84%

Ph

Boc

S

N

6r, 70%

6p, 76%

6q, 82%

Ph

N

Ph

N

Ph

6t, 66%

6s, 70%

L:

Scheme 6 Substrate scope of aryl bromides for the synthesis of triaryl-

methanes. Reactions were carried out with 5a (0.36 mmol), 2 (0.3

mmol), in the presence of Pd(OAc)₂(5 mol%), L (15 mol%), HCO₂NH₄

(0.36 mmol), MeCO₂NH₄(0.45 mmol), and Cs₂CO₃(0.6 mmol) in tert-

pentyl alcohol (3.0 mL) at 90 °C for 4 h. Yields refer to isolated products

by silica gel column chromatography.

NNHTs

Ph₂P

Ph

Pd(OAc)₂(5 mol%), L (15 mol%)

Ph

5a

+

HCO₂NH₄(1.2 equiv)

^tBu

Cs₂CO₃(2.0 equiv)

^tBu

Br

MeCO₂NH₄(1.5 equiv)

tert-pentanol, 90 °C, 4 h

6a, 91%

Finally, the reductive coupling reactions with a range of

diarylmethanone N-tosylhydrazones as the substrate were

explored, affording the corresponding triarylmethanes in

moderate to good yields (Scheme 7). It was worth noting

that the product 7h could not be obtained through the tra-

ditional Friedel–Crafts reactions. Moreover, the diarylmeth-

anone N-tosylhydrazones containing heterocyclic moieties

2b

Scheme 5 Optimized conditions for the preparation of triarylmethane

6a

With the optimized reaction conditions, benzophenone

N-tosylhydrazone 5a and a series of aryl bromides were

used as the substrates to examine the scope of this reaction.

E

Y. Xia et al.

Paper

Synthesis

strate D in situ, followed by the formation of Pd carbene in-

termediate E. Migratory insertion of Pd carbene E affords

species F, followed by hydrogen transfer from i-PrOH or

HCO₂NH₄to give the palladium-hydride complex G. Finally,

the product P is produced through the reductive elimina-

tion of the intermediate G, with simultaneous regeneration

of Pd(0) catalyst. In this transformation, the major by-prod-

uct C is generated by the direct reduction of the intermedi-

ate B. In the case of triarylmethane synthesis, the side reac-

tion can be minimized by adding ammonium acetate as the

additive.¹³

In summary, we have developed a novel reaction for the

synthesis of di- and triarylmethanes through Pd-catalyzed

reductive coupling of N-tosylhydrazones with aryl halides.

This reaction utilized N-tosylhydrazones as the alkyl metal-

lic reagent equivalents to form the C–C single bonds. The

reaction tolerates various functional groups. The reaction

with substrates containing heterocyclic moiety also pro-

ceeded well. It is thus expected that the reaction may find

applications in the synthesis of related compounds.

Pd(OAc)₂(5 mol%), L (15 mol%)

Ar¹

Ar²

Ar¹

HCO₂NH₄(1.2 equiv)

Ar³

NNHTs

Ar²

+

Ar³Br

Cs₂CO₃(2.0 equiv)

MeCO₂NH₄(1.5 equiv)

tert-pentanol, 90 °C, 4 h

7a–l

2

1b–k

Ph

MeO

Me

^tBu

EtO

^tBu

Ph

7b, 72%

Ph

7a, 81%

7c, 79%

Me

Cl

^tBu

Ph

7f, 48%

Me

Cl

7e, 58%

7d, 80%

All the palladium-catalyzed reactions were performed under argon

atmosphere in a flame-dried reaction flask. All solvents were distilled

under N₂atmosphere prior to use. 1,4-Dioxane and toluene were

dried over Na with benzophenone-ketyl intermediate as indicator,

and tert-pentyl alcohol, DCE, MeCN were dried over CaH₂. i-PrOH was

dried over anhyd Na₂SO₄. HCO₂NH₄and MeCO₂NH₄were used after

drying under vacuum at r.t. for 24 h. For chromatography, 200–300

mesh silica gel (Qingdao, China) was employed. ¹H and ¹³C NMR spec-

tra were recorded at 400 MHz and 100 MHz with Bruker ARX 400

spectrometer. Chemical shifts are reported in ppm using TMS as an

internal standard. IR spectra were recorded with a Nicolet 5MX-S IR

spectrometer. LRMS were recorde on an Agilent 5975C inert 350 EI

mass spectrometer. HRMS data were recorded on a Bruker Apex IV

FTMS by ESI or GCT CA127 Micronass UK by EI.

Me

^tBu

Me

N

MeO

Ph

7i, 72%

OMe

7g, 74%

7h, 83%

Me

O

S

Aromatic Aldehyde N-Tosylhydrazones 1a–f; Benzaldehyde

N-Tosylhydrazone 1a; Typical Procedure 1

N

^tBu

To a solution of benzaldehyde (3.18 g, 30 mmol) in MeOH (25 mL) was

added TsNHNH₂(5.58 g, 30 mmol). The resulting mixture was heated

to 60 °C and stirred for 5 h. After completion of the reaction, the mix-

ture was cooled to r.t., the precipitate was collected by filtration, and

washed with PE. The precipitate was dried in a desiccator under vacu-

um to afford the pure product 1a (6.98 g, 85%). The yields for other

tosylhydrazones 1b–f were about 73–88%. The reactions were usually

carried out overnight and were monitored by TLC.

Ph

7l, 30%

7k, 42%

7j, 51%

Me

Scheme 7 Substrate scope of N-tosylhydrazones for the synthesis of

triarylmethanes. Reactions were carried out with 1 (0.36 mmol), 2 (0.3

mmol), in the presence of Pd(OAc)₂(5 mol%), L (15 mol%), HCO₂NH₄

(0.36 mmol), MeCO₂NH₄(0.45 mmol), and Cs₂CO₃(0.6 mmol) in tert-

pentyl alcohol (3.0 mL) at 90 °C for 4 h. All the yields refer to isolated

products by silica gel column chromatography.

Diarylmethanone N-Tosylhydrazones 5a–k; Benzophenone

N-Tosylhydrazone 5a; Typical Procedure 2

To a solution of benzophenone (7.28 g, 40 mmol) in EtOH (30 mL)

were added TsNHNH₂(7.44 g, 40 mmol) and TsOH·H₂O (76 mg, 0.4

mmol, 1 mol%). The resulting mixture was refluxed for 5 h. After com-

pletion of the reaction, the mixture was cooled to r.t., the precipitate

was collected by filtration, and washed with PE. The precipitate was

dried in a desiccator under vacuum to afford the pure product 5a

(13.12 g, 94%). The yields for other tosylhydrazones 5b–k were about

75–95%. The reactions were usually carried out overnight and were

monitored by TLC.

were also found as suitable substrates in the reactions (7i–

l).

Based on our understanding of the palladium-catalyzed

coupling reaction of N-tosylhydrazones,⁸we propose a pos-

sible mechanism as shown in Scheme 8. First, Pd(0)L A is

oxidized to Pd(II) species B by aryl bromides. Then treat-

ment of N-tosylhydrazone with base generates diazo sub-

F

Y. Xia et al.

Paper

Synthesis

Ar²

X

Ar¹

R

2

Pd(0)L

A

P

reductive

elimination

oxidative addition

direct reduction

X

Ar²

Ar¹

[H]

Ar²Pd(II)L

Ar²

H

G

LHPd

B

R

C

N₂

O

carbene formation

hydrogen

transfer

Ar¹

R

X

+

Me

D

base

X

Ar²Pd(II)L

Ar²

LXPd

Ar¹

NNHTs

R

Me

O

migratory

insertion

Ar¹

H

Ar¹

R

F

E

Scheme 8 Proposed reaction mechanism

Palladium-Catalyzed Reductive Coupling Reaction for the Synthe-

sis of Diarylmethanes; 4-Benzyl-1,1′-biphenyl (3a); Typical Proce-

dure 3

1-Benzyl-4-methylbenzene (3d)^3d

The title compound was prepared following typical procedure 3. After

purification by silica gel column chromatography (eluent: PE), the

product was isolated as a colorless oil (34 mg, 63%).

¹H NMR (400 MHz, CDCl₃): δ = 7.29–7.24 (m, 2 H), 7.19–7.15 (m, 3 H),

7.11–7.05 (m, 4 H), 3.92 (s, 2 H), 2.30 (s, 3 H).

¹³C NMR (100 MHz, CDCl₃): δ = 141.3, 138.0, 135.5, 129.1, 128.8,

Under an argon atmosphere, Pd(OAc)₂(3.3 mg, 0.015 mmol, 5 mol%),

PCy₃·HBF₄(22.1 mg, 0.06 mmol, 20 mol%), benzaldehyde N-tosylhy-

drazone 1a (99 mg, 0.36 mmol), 4-bromo-1,1′-biphenyl (2a; 70 mg,

0.3 mmol), and Cs₂CO₃(195 mg, 0.6 mmol) were successively added

to a flame-dried 25 mL Schlenk flask. The reaction flask was degassed

three times with argon. Then anhyd toluene (2.7 mL) and i-PrOH (0.3

mL) were added with a syringe. Note that the aryl bromide in oil form

was added to the reaction flask prior to i-PrOH. The reaction was

heated at 80 °C with stirring for about 12 h, then it was cooled to r.t.,

and filtered through a short pad of neutral alumina with EtOAc (25

mL) as eluent. Solvent was then removed in vacuo to leave a crude

mixture, which was purified by silica gel column chromatography

(eluent: PE) to give 3a^3das a white solid (59 mg, 80%); mp 84–85 °C.

128.7, 128.4, 125.9, 41.4, 20.9.

1-Benzyl-4-methoxybenzene (3e)^3d

The title compound was prepared following typical procedure 3. After

purification by silica gel column chromatography (eluent: PE–EtOAc,

100:1), the product was isolated as a colorless oil (44 mg, 74%).

¹H NMR (400 MHz, CDCl₃): δ = 7.21–7.17 (m, 2 H), 7.12–7.07 (m, 3 H),

7.02 (d, J = 8.4 Hz, 2 H), 6.74 (d, J = 8.4 Hz, 2 H), 3.82 (s, 2 H), 3.68 (s, 3

H).

¹H NMR (400 MHz, CDCl₃): δ = 7.57–7.55 (m, 2 H), 7.52–7.49 (m, 2 H),

7.43–7.38 (m, 2 H), 7.33–7.19 (m, 8 H), 4.00 (s, 2 H).

¹³C NMR (100 MHz, CDCl₃): δ = 140.9, 140.2, 139.0, 129.2, 128.9,

¹³C NMR (100 MHz, CDCl₃): δ = 157.9, 141.5, 133.2, 129.8, 128.7,

128.3, 125.9, 113.8, 55.2, 40.9.

128.6, 128.4, 127.1, 127.0, 126.9, 126.1, 41.5.

1-Benzyl-4-(trifluoromethyl)benzene (3f)^3d

Benzyl-4-(tert-butyl)benzene (3b)^6c

The title compound was prepared following typical procedure 3. After

purification by silica gel column chromatography (eluent: PE), the

product was isolated as a colorless oil (47 mg, 67%).

¹H NMR (400 MHz, CDCl₃): δ = 7.52 (d, J = 8.0 Hz, 2 H), 7.32–7.27 (m, 4

The title compound was prepared following typical procedure 3. After

purification by silica gel column chromatography (eluent: PE), the

product was isolated as a colorless oil (47 mg, 71%).

¹H NMR (400 MHz, CDCl₃): δ = 7.31–7.25 (m, 4 H), 7.21–7.18 (m, 3 H),

7.11 (d, J = 8.4 Hz, 2 H), 3.94 (s, 2 H), 1.29 (s, 9 H).

¹³C NMR (100 MHz, CDCl₃): δ = 148.8, 141.2, 138.0, 128.9, 128.5,

128.4, 125.9, 125.3, 41.4, 34.3, 31.3.

H), 7.24–7.15 (m, 3 H), 4.02 (s, 2 H).

¹³C NMR (100 MHz, CDCl₃): δ = 145.1, 139.9, 129.1, 128.9, 128.6,

128.4 (q, J = 32.1 Hz), 126.4, 125.3 (q, J = 3.7 Hz), 124.3 (q, J = 271.6

Hz), 41.6.

Diphenylmethane (3c)^3d

1-Benzyl-4-fluorobenzene (3g)^3d

The title compound was prepared following typical procedure 3. After

purification by silica gel column chromatography (eluent: PE), the

product was isolated as a colorless oil (33 mg, 66%).

The title compound was prepared following typical procedure 3. After

purification by silica gel column chromatography (eluent: PE), the

product was isolated as a colorless oil (41 mg, 73%).

¹H NMR (400 MHz, CDCl₃): δ = 7.29–7.28 (m, 4 H), 7.19–7.16 (m, 6 H),

¹H NMR (400 MHz, CDCl₃): δ = 7.31–7.26 (m, 2 H), 7.22–7.10 (m, 5 H),

3.96 (s, 2 H).

6.97–6.93 (m, 2 H), 3.94 (s, 2 H).

¹³C NMR (100 MHz, CDCl₃): δ = 141.0, 128.9, 128.4, 126.0, 41.9.

¹³C NMR (100 MHz, CDCl₃): δ = 161.4 (d, J = 242.6 Hz), 140.9, 136.7 (d,

J = 3.0 Hz), 130.2 (d, J = 7.8 Hz), 128.8, 128.5, 126.1, 115.1 (d, J = 21.1

Hz), 41.0.

G

Y. Xia et al.

Paper

Synthesis

Methyl 4-Benzylbenzoate (3h)^6f

5-Benzyl-2-methoxy-1,3-dimethylbenzene (3n)¹⁴

The title compound was prepared following typical procedure 3. After

purification by silica gel column chromatography (eluent: PE–EtOAc,

50:1), the product was isolated as a yellow oil (41 mg, 61%).

The title compound was prepared following typical procedure 3. After

purification by silica gel column chromatography (eluent: PE–EtOAc,

100:1), the product was isolated as a colorless oil (42 mg, 62%).

¹H NMR (400 MHz, CDCl₃): δ = 7.95 (d, J = 7.2 Hz, 2 H), 7.31–7.20 (m, 5

H), 7.16 (d, J = 7.6 Hz, 2 H), 4.01 (s, 2 H), 3.88 (s, 3 H).

¹H NMR (400 MHz, CDCl₃): δ = 7.22–7.17 (m, 2 H), 7.12–7.09 (m, 3 H),

6.74 (s, 2 H), 3.77 (s, 2 H), 3.60 (s, 3 H), 2.15 (s, 6 H).

¹³C NMR (100 MHz, CDCl₃): δ = 167.0, 146.4, 140.0, 129.7, 128.9,

¹³C NMR (100 MHz, CDCl₃): δ = 155.2, 141.4, 136.3, 130.6, 129.1,

128.5, 128.0, 126.3, 51.9, 41.8.

128.8, 128.3, 125.9, 59.6, 41.3, 16.0.

1-(4-Benzylphenyl)ethanone (3i)^6d

2-Benzylnaphthalene (3o)^6b

The title compound was prepared following typical procedure 3. After

purification by silica gel column chromatography (eluent: PE–EtOAc,

30:1), the product was isolated as a colorless oil (44 mg, 70%).

The title compound was prepared following typical procedure 3. After

purification by silica gel column chromatography (eluent: PE), the

product was isolated as a colorless oil (38 mg, 58%).

¹H NMR (400 MHz, CDCl₃): δ = 7.87 (d, J = 8.4 Hz, 2 H), 7.31–7.16 (m, 7

¹H NMR (400 MHz, CDCl₃): δ = 7.79–7.72 (m, 3 H), 7.61 (s, 1 H), 7.44–

H), 4.02 (s, 2 H), 2.56 (s, 3 H).

7.40 (m, 2 H), 7.31–7.19 (m, 6 H), 4.12 (s, 2 H).

¹³C NMR (100 MHz, CDCl₃): δ = 197.7, 146.7, 139.9, 135.2, 129.0,

¹³C NMR (100 MHz, CDCl₃): δ = 140.9, 138.5, 133.5, 132.0, 129.0,

128.8, 128.5, 126.3, 41.8, 26.5.

128.4, 128.0, 127.7, 127.6, 127.5, 127.0, 126.1, 125.9, 125.3, 42.0.

(4-Benzylphenyl)trimethylsilane (3j)^6c

1-Benzylnaphthalene (3p)^6e

The title compound was prepared following typical procedure 3. After

purification by silica gel column chromatography (eluent: PE), the

product was isolated as a colorless oil (47 mg, 65%).

The title compound was prepared following typical procedure 3. After

purification by silica gel column chromatography (eluent: PE), the

product was isolated as a colorless oil (33 mg, 50%).

¹H NMR (400 MHz, CDCl₃): δ = 7.44 (d, J = 7.6 Hz, 2 H), 7.30–7.25 (m, 2

H), 7.21–7.16 (m, 5 H), 3.96 (s, 2 H), 0.24 (s, 9 H).

¹³C NMR (100 MHz, CDCl₃): δ = 141.7, 140.9, 137.7, 133.5, 128.9,

128.4, 128.3, 126.0, 41.9, -1.0.

¹H NMR (400 MHz, CDCl₃): δ = 7.99–7.96 (m, 1 H), 7.86–7.83 (m, 1 H),

7.74 (d, J = 8.0 Hz, 1 H), 7.46–7.38 (m, 3 H), 7.29–7.23 (m, 3 H), 7.21–

7.17 (m, 3 H), 4.43 (s, 2 H).

¹³C NMR (100 MHz, CDCl₃): δ = 140.6, 136.6, 133.9, 132.1, 128.7,

128.6, 128.4, 127.3, 127.1, 126.0, 125.9, 125.5, 124.2, 39.0.

1-Benzyl-3-methoxybenzene (3k)^6b

3-Benzylpyridine (3q)¹⁵

The title compound was prepared following typical procedure 3. After

purification by silica gel column chromatography (eluent: PE–EtOAc,

100:1), the product was isolated as a colorless oil (47 mg, 80%).

¹H NMR (400 MHz, CDCl₃): δ = 7.29–7.25 (m, 2 H), 7.23–7.17 (m, 4 H),

6.78 (d, J = 7.2 Hz, 1 H), 6.75–6.72 (m, 2 H), 3.94 (s, 2 H), 3.75 (s, 3 H).

The title compound was prepared following typical procedure 3. After

purification by silica gel column chromatography (eluent: PE–EtOAc,

5:1), the product was isolated as a colorless oil (38 mg, 75%).

¹H NMR (400 MHz, CDCl₃): δ = 8.51–8.44 (m, 2 H), 7.45 (d, J = 7.6 Hz, 1

H), 7.35–7.27 (m, 2 H), 7.24–7.16 (m, 4 H), 3.97 (s, 2 H).

¹³C NMR (100 MHz, CDCl₃): δ = 150.1, 147.5, 139.7, 136.4, 136.2,

¹³C NMR (100 MHz, CDCl₃): δ = 159.6, 142.6, 140.8, 129.3, 128.8,

128.4, 126.0, 121.3, 114.7, 111.2, 55.0, 41.9.

128.7, 128.6, 126.4, 123.3, 38.9.

1-Benzyl-2-methoxybenzene (3l)^5c

3-Benzylquinoline (3r)¹⁶

The title compound was prepared following typical procedure 3. After

purification by silica gel column chromatography (eluent: PE–EtOAc,

100:1), the product was isolated as a colorless oil (44 mg, 74%).

¹H NMR (400 MHz, CDCl₃): δ = 7.28–7.16 (m, 6 H), 7.06 (d, J = 6.8 Hz, 1

The title compound was prepared following typical procedure 3. After

purification by silica gel column chromatography (eluent: PE–EtOAc,

10:1), the product was isolated as a colorless oil (53 mg, 81%).

H), 6.89–6.84 (m, 2 H), 3.97 (s, 2 H), 3.80 (s, 3 H).

¹³C NMR (100 MHz, CDCl₃): δ = 157.3, 141.0, 130.2, 129.6, 128.9,

128.2, 127.3, 125.7, 120.4, 110.3, 55.3, 35.8.

¹H NMR (400 MHz, CDCl₃): δ = 8.81 (d, J = 2.0 Hz, 1 H), 8.08 (d, J = 8.4

Hz, 1 H), 7.87 (d, J = 0.8 Hz, 1 H), 7.71 (d, J = 8.4 Hz, 1 H), 7.67–7.62 (m,

1 H), 7.52–7.47 (m, 1 H), 7.33–7.28 (m, 2 H), 7.25–7.20 (m, 3 H), 4.14

(s, 2 H).

¹³C NMR (100 MHz, CDCl₃): δ = 152.0, 146.8, 139.6, 134.7, 133.7,

129.1, 128.8, 128.7, 128.6, 128.0, 127.3, 126.5, 126.4, 39.1.

4-Benzyl-1,2-dimethylbenzene (3m)^3c

The title compound was prepared following typical procedure 3. After

purification by silica gel column chromatography (eluent: PE), the

product was isolated as a colorless oil (35 mg, 60%).

tert-Butyl 5-Benzyl-1H-indole-1-carboxylate (3s)

The title compound was prepared following typical procedure 3. After

purification by silica gel column chromatography (eluent: PE–EtOAc,

60:1), the product was isolated as a colorless oil (50 mg, 54%).

¹H NMR (400 MHz, CDCl₃): δ = 7.29–7.24 (m, 2 H), 7.21–7.17 (m, 3 H),

7.04 (d, J = 7.6 Hz, 1 H), 6.95 (s, 1 H), 6.91 (d, J = 7.6 Hz, 1 H), 3.90 (s, 2

H), 2.21 (s, 6 H).

¹³C NMR (100 MHz, CDCl₃): δ = 141.5, 138.5, 136.5, 134.1, 130.2,

129.6, 128.8, 128.3, 126.2, 125.9, 41.5, 19.7, 19.2.

IR (film): 1731, 1470, 1371, 1346, 1161, 1128, 1023, 726, 698 cm^–1

.

¹H NMR (400 MHz, CDCl₃): δ = 8.03 (d, J = 8.0 Hz, 1 H), 7.55 (d, J = 3.2

Hz, 1 H), 7.35–7.13 (m, 7 H), 6.48 (d, J = 3.6 Hz, 1 H), 4.05 (s, 2 H), 1.64

(s, 9 H).

H

Y. Xia et al.

Paper

Synthesis

¹³C NMR (100 MHz, CDCl₃): δ = 149.7, 141.6, 135.4, 133.7, 130.8,

1-(tert-Butyl)-4-(4-methoxybenzyl)benzene (4d)

128.8, 128.3, 126.0, 125.9, 125.4, 120.9, 115.0, 107.1, 83.4, 41.7, 28.1.

LRMS (EI): m/z = 207 [(M – 100)⁺, 100], 191 (10), 178 (22), 165 (8),

130 (50).

The title compound was prepared following typical procedure 3. After

purification by silica gel column chromatography (eluent: PE–EtOAc,

100:1), the product was isolated as a colorless oil (31 mg, 41%).

IR (film): 1510, 1246, 1176, 1037, 815, 653 cm^–1

.

HRMS (ESI): m/z calcd for C₂₀H₂₂NO₂[M + H]⁺: 308.1645; found:

¹H NMR (400 MHz, CDCl₃): δ = 7.29 (d, J = 8.4 Hz, 2 H), 7.11 (d, J = 8.8

Hz, 2 H), 7.09 (d, J = 8.4 Hz, 2 H), 6.82 (d, J = 8.8 Hz, 2 H), 3.88 (s, 2 H),

3.77 (s, 3 H), 1.29 (s, 9 H).

308.1638.

5-Benzylbenzo[b]thiophene (3t)¹⁶

¹³C NMR (100 MHz, CDCl₃): δ = 157.8, 148.7, 138.5, 133.4, 129.8,

128.3, 125.2, 113.8, 55.2, 40.4, 34.3, 31.3.

LRMS (EI): m/z = 254 (M⁺, 52), 239 (100), 197 (20), 165 (10).

HRMS (EI): m/z calcd for C₁₄H₁₅O [M]⁺: 254.1665; found: 254.1674.

The title compound was prepared following typical procedure 3. After

purification by silica gel column chromatography (eluent: PE), the

product was isolated as a colorless oil (35 mg, 52%).

¹H NMR (400 MHz, CDCl₃): δ = 7.77 (d, J = 8.4 Hz, 1 H), 7.61 (d, J = 0.4

Hz, 1 H), 7.39 (d, J = 5.6 Hz, 1 H), 7.30–7.16 (m, 7 H), 4.09 (s, 2 H).

¹³C NMR (100 MHz, CDCl₃): δ = 141.2, 139.9, 137.5, 137.2, 128.9,

128.4, 126.5, 126.0, 125.7, 123.6, 123.5, 122.3, 41.8.

4-(4-Methoxybenzyl)-1,1′-biphenyl (4e)^5b

The title compound was prepared following typical procedure 3. After

purification by silica gel column chromatography (eluent: PE–EtOAc,

100:1), the product was isolated as a colorless oil (40 mg, 48%).

Di([1,1′-Biphenyl]-4-yl)methane (4a)¹⁷

The title compound was prepared following typical procedure 3. After

purification by silica gel column chromatography (eluent: PE), the

product was isolated as a colorless oil (63 mg, 66%).

¹H NMR (400 MHz, CDCl₃): δ = 7.59–7.51 (m, 8 H), 7.43–7.39 (m, 4 H),

7.33–7.27 (m, 6 H), 4.05 (s, 2 H).

¹³C NMR (100 MHz, CDCl₃): δ = 140.9, 140.1, 139.1, 129.3, 128.7,

¹H NMR (400 MHz, CDCl₃): δ = 7.57–7.54 (m, 2 H), 7.50 (d, J = 8.4 Hz, 2

H), 7.43–7.38 (m, 2 H), 7.33–7.28 (m, 1 H), 7.25–7.21 (m, 2 H), 7.13 (d,

J = 8.4 Hz, 2 H), 6.85–6.82 (m, 2 H), 3.95 (s, 2 H), 3.77 (s, 3 H).

¹³C NMR (100 MHz, CDCl₃): δ = 158.0, 141.0, 140.6, 138.9, 133.1,

129.8, 129.1, 128.6, 127.1, 127.0, 126.9, 113.9, 55.2, 40.6.

127.2, 127.0, 126.9, 41.2.

5-[4-(tert-Butyl)benzyl]benzo[d][1,3]dioxole (4f)

The title compound was prepared following typical procedure 3. After

purification by silica gel column chromatography (eluent: PE–EtOAc,

60:1), the product was isolated as a colorless oil (40 mg, 50%).

4-[4-(tert-Butyl)benzyl]-1,1′-biphenyl (4b)

The title compound was prepared following typical procedure 3. After

purification by silica gel column chromatography (eluent: PE), the

product was isolated as a white solid (58 mg, 64%); mp 46–47 °C.

IR (film): 1513, 1487, 1363, 1267, 1109, 1008, 760, 697 cm^–1

¹H NMR (400 MHz, CDCl₃): δ = 7.57–7.54 (m, 2 H), 7.50 (d, J = 8.0 Hz, 2

H), 7.43–7.38 (m, 2 H), 7.33–7.25 (m, 5 H), 7.15 (d, J = 8.4 Hz, 2 H),

3.98 (s, 2 H), 1.30 (s, 9 H).

¹³C NMR (100 MHz, CDCl₃): δ = 148.8, 141.0, 140.4, 138.9, 137.9,

129.3, 128.6, 128.5, 127.1, 127.0, 126.9, 125.3, 41.0, 34.3, 31.3.

LRMS (EI): m/z = 300 (M⁺, 55), 285 (100), 243 (8), 207 (5), 167 (42).

HRMS (ESI): m/z calcd for C₂₃H₂₄Na [M + Na]⁺: 323.1770; found:

IR (film): 1502, 1442, 1244, 1040, 941, 797 cm^–1

.

¹H NMR (400 MHz, CDCl₃): δ = 7.29 (d, J = 8.0 Hz, 2 H), 7.10 (d, J = 8.0

Hz, 2 H), 6.72 (d, J = 8.4 Hz, 1 H), 6.68–6.66 (m, 2 H), 5.89 (s, 2 H), 3.85

(s, 2 H), 1.29 (s, 9 H).

¹³C NMR (100 MHz, CDCl₃): δ = 148.8, 147.6, 145.7, 138.1, 135.1,

128.3, 125.3, 121.6, 109.4, 108.1, 100.7, 41.0, 34.3, 31.3.

LRMS (EI): m/z = 268 (M⁺, 58), 253 (100), 225 (6), 211 (15), 135 (29).

HRMS (ESI): m/z calcd for C₁₈H₂₀O₂Na [M + Na]⁺: 291.1355; found:

.

291.1359.

323.1776.

5-(4-Methoxybenzyl)benzo[d][1,3]dioxole (4g)

The title compound was prepared following typical procedure 3. After

purification by silica gel column chromatography (eluent: PE–EtOAc,

60:1), the product was isolated as a colorless oil (31 mg, 43%).

4-(4-Fluorobenzyl)-1,1′-biphenyl (4c)

The title compound was prepared following typical procedure 3. After

purification by silica gel column chromatography (eluent: PE), the

product was isolated as a white solid (41 mg, 52%): mp 83–84 °C.

IR (film): 1507, 1488, 1218, 1157, 747, 687 cm^–1

¹H NMR (400 MHz, CDCl₃): δ = 7.58–7.54 (m, 2 H), 7.51 (d, J = 8.0 Hz, 2

H), 7.43–7.39 (m, 2 H), 7.34–7.29 (m, 1 H), 7.22 (d, J = 8.0 Hz, 2 H),

7.18–7.14 (m, 2 H), 7.00–6.95 (m, 2 H), 3.97 (s, 2 H).

¹³C NMR (100 MHz, CDCl₃): δ = 161.4 (d, J = 242.6 Hz), 140.8, 140.0,

139.1, 136.6 (d, J = 3.3 Hz), 130.3 (d, J = 7.8 Hz), 129.2, 128.7, 127.2,

127.1, 126.9, 115.2 (d, J = 21.1 Hz), 40.7.

IR (film): 1511, 1488, 1245, 1038, 815, 667 cm^–1

.

¹H NMR (400 MHz, CDCl₃): δ = 7.08 (d, J = 8.4 Hz, 2 H), 6.84–6.81 (m, 2

H), 6.72 (d, J = 8.4 Hz, 1 H), 6.65–6.62 (m, 2 H), 5.89 (s, 2 H), 3.82 (s, 2

H), 3.77 (s, 3 H).

¹³C NMR (100 MHz, CDCl₃): δ = 157.9, 147.6, 145.7, 135.4, 133.3,

129.6, 121.5, 113.8, 109.2, 108.0, 100.7, 55.2, 40.6.

LRMS (EI): m/z = 242 (M⁺, 100), 227 (7), 211 (47), 197 (20), 181 (22).

HRMS (EI): m/z calcd for C₁₄H₁₅O [M]⁺: 242.0937; found: 242.0938.

.

LRMS (EI): m/z = 262 (M⁺, 100), 247 (10), 233 (6), 207 (7), 183 (15),

165 (27).

Methyl 4-([1,1′-Biphenyl]-4-ylmethyl)benzoate (4h)

The title compound was prepared following typical procedure 3. After

purification by silica gel column chromatography (eluent: PE–EtOAc,

100:1), the product was isolated as a white solid (35 mg, 38%); mp

98–99 °C.

HRMS (EI): m/z calcd for C₁₄H₁₅O [M]⁺: 262.1152; found: 262.1158.

I

Y. Xia et al.

Paper

Synthesis

IR (film): 1714, 1435, 1278, 1109, 757, 694 cm^–1

.

dried 25 mL Schlenk flask. The reaction flask was degassed three

times with argon and anhyd tert-pentyl alcohol (3.0 mL) was added

using a syringe. Then 1-bromo-4-(tert-butyl)benzene (2b; 64 mg, 0.3

mmol) was added with a syringe. Note that the aryl bromide in a solid

form was added to the reaction flask prior to Cs₂CO₃. The reaction

was heated at 90 °C with stirring for about 4 h, then it was cooled to

r.t., and filtered through a short pad of neutral alumina with EtOAc

(25 mL) as eluent. Solvent was then removed in vacuo to leave a crude

mixture, which was purified by silica gel column chromatography

(eluent: PE); yellow solid (82 mg, 91%).

¹H NMR (400 MHz, CDCl₃): δ = 7.97 (d, J = 8.4 Hz, 2 H), 7.58–7.55 (m, 2

H), 7.52 (d, J = 8.4 Hz, 2 H), 7.44–7.39 (m, 2 H), 7.34–7.22 (m, 5 H),

4.05 (s, 2 H), 3.89 (s, 3 H).

¹³C NMR (100 MHz, CDCl₃): δ = 167.0, 146.3, 140.8, 139.3, 139.1,

129.8, 129.3, 128.9, 128.7, 128.1, 127.3, 127.1, 126.9, 51.9, 41.5.

LRMS (EI): m/z = 302 (M⁺, 100), 271 (24), 243 (47), 228 (10), 207 (13),

165 (40).

HRMS (ESI): m/z calcd for C₂₁H₁₉O₂[M + H]⁺: 303.1379; found:

303.1377.

¹H NMR (400 MHz, CDCl₃): δ = 7.30–7.25 (m, 6 H), 7.22–7.18 (m, 2 H),

7.12 (d, J = 7.6 Hz, 4 H), 7.03 (d, J = 8.2 Hz, 2 H), 5.51 (s, 1 H), 1.30 (s, 9

H).

Methyl 4-[4-(tert-Butyl)benzyl]benzoate (4i)

The title compound was prepared following typical procedure 3. After

purification by silica gel column chromatography (eluent: PE–EtOAc,

100:1), the product was isolated as a colorless oil (36 mg, 43%).

¹³C NMR (100 MHz, CDCl₃): δ = 148.9, 144.1, 140.7, 129.4, 128.9,

128.2, 126.1, 125.1, 56.3, 34.3, 31.3.

Triphenylmethane (6b)¹⁸

IR (film): 1722, 1609, 1434, 1277 1110, 1020, 758 cm^–1

.

¹H NMR (400 MHz, CDCl₃): δ = 7.95 (d, J = 7.2 Hz, 2 H), 7.31 (d, J = 7.2

Hz, 2 H), 7.26 (d, J = 7.6 Hz, 2 H), 7.09 (d, J = 7.6 Hz, 2 H), 3.99 (s, 2 H),

3.89 (s, 3 H), 1.29 (s, 9 H).

¹³C NMR (100 MHz, CDCl₃): δ = 167.0, 149.1, 146.6, 137.0, 129.7,

128.9, 128.5, 128.0, 125.4, 51.9, 41.4, 34.3, 31.3.

The title compound was prepared following typical procedure 4. After

purification by silica gel column chromatography (eluent: PE), the

product was isolated as a white solid (59 mg, 81%); mp 93–94 °C.

¹H NMR (400 MHz, CDCl₃): δ = 7.29–7.26 (m, 6 H), 7.22–7.18 (m, 3 H),

7.12–7.10 (m, 6 H), 5.55 (s, 1 H).

¹³C NMR (100 MHz, CDCl₃): δ = 143.8, 129.4, 128.2, 126.2, 56.7.

LRMS (EI): m/z = 282 (M⁺, 22), 267 (100), 251 (8), 207 (11), 165 (12).

HRMS (ESI): m/z calcd for C₁₉H₁₃O₂[M + H]⁺: 283.1693; found:

283.1695.

(p-Tolylmethylene)dibenzene (6c)^7f

The title compound was prepared following typical procedure 4. After

purification by silica gel column chromatography (eluent: PE), the

product was isolated as a white solid (58 mg, 75%); mp 67–68 °C.

¹H NMR (400 MHz, CDCl₃): δ = 7.28–7.16 (m, 6 H), 7.12–7.07 (m, 6 H),

7.01–6.99 (m, 2 H), 5.51 (s, 1 H), 2.30 (s, 3 H).

¹³C NMR (100 MHz, CDCl₃): δ = 144.0, 140.8, 135.7, 129.3, 129.2,

1-(tert-Butyl)-4-(4-methylbenzyl)benzene (4j)^3a

The title compound was prepared following typical procedure 3. After

purification by silica gel column chromatography (eluent: PE), the

product was isolated as a colorless oil (38 mg, 53%).

¹H NMR (400 MHz, CDCl₃): δ = 7.32–7.27 (m, 2 H), 7.14–7.08 (m, 6 H),

128.9, 128.2, 126.1, 56.4, 20.9.

3.90 (s, 2 H), 2.30 (s, 3 H), 1.28 (s, 9 H).

¹³C NMR (100 MHz, CDCl₃): δ = 148.7, 138.3, 138.2, 135.4, 129.1,

128.8, 128.4, 125.3, 40.9, 34.3, 31.3, 20.9.

4-Benzhydryl-1,1′-biphenyl (6d)^7f

The title compound was prepared following typical procedure 4. After

purification by silica gel column chromatography (eluent: PE), the

product was isolated as a yellow solid (77 mg, 80%); mp 111–112 °C.

¹H NMR (400 MHz, CDCl₃): δ = 7.57–7.55 (m, 2 H), 7.50 (d, J = 8.2 Hz, 2

H), 7.42–7.38 (m, 2 H), 7.32–7.14 (m, 13 H), 5.58 (s, 1 H).

¹³C NMR (100 MHz, CDCl₃): δ = 143.7, 142.9, 140.7, 139.1, 129.8,

4-Benzyl-1,1′-biphenyl (3a); Gram-Scale Procedure

Under an argon atmosphere, Pd(OAc)₂(0.056 g, 0.25 mmol, 5 mol%),

PCy₃·HBF₄(0.375 g, 1.0 mmol, 20 mol%), benzaldehyde N-tosylhydra-

zone 1a (1.65 g, 6 mmol), and Cs₂CO₃(3.28 g, 10.0 mmol) were suc-

cessively added to a flame-dried 250 mL Schlenk flask. The reaction

flask was degassed three times with argon and anhyd toluene (50.0

mL) was added using a syringe. Then 4-bromo-1,1′-biphenyl (2a; 1.17

g, 5.0 mmol) and i-PrOH (5.0 mL) were added with a syringe. Note

that the aryl bromide in a solid form was added to the reaction flask

prior to Cs₂CO₃. The reaction mixture heated at 80 °C with stirring for

about 12 h, then cooled to r.t., and filtered through a short pad of neu-

tral alumina with EtOAc (200 mL) as eluent. Solvent was then re-

moved in vacuo to leave a crude mixture. After purification by silica

gel column chromatography (eluent: PE), 4-benzyl-1,1′-biphenyl (3a)

was isolated as a white solid (0.768 g, 63%).

129.4, 128.7, 128.3, 127.1, 126.9, 126.3, 56.4.

[(4-Methoxyphenyl)methylene]dibenzene (6e)^7f

The title compound was prepared following typical procedure 4. After

purification by silica gel column chromatography (eluent: PE), the

product was isolated as a yellow solid (66 mg, 80%); mp 64–65 °C.

¹H NMR (400 MHz, CDCl₃): δ = 7.29–7.28 (m, 3 H), 7.21 (t, J = 7.2 Hz, 3

H), 7.11 (d, J = 7.2 Hz, 4 H), 7.02 (d, J = 8.6 Hz, 2 H), 6.82 (d, J = 8.6 Hz,

2 H), 5.50 (s, 1 H), 3.77 (s, 3 H).

¹³C NMR (100 MHz, CDCl₃): δ = 157.9, 144.2, 136.0, 130.3, 129.3,

128.2, 126.1, 113.6, 55.9, 55.1.

Palladium-Catalyzed Reductive Coupling Reaction for the Synthe-

sis of Triarylmethanes; {[4-(tert-Butyl)phenyl]methylene}diben-

zene (6a);^7cTypical Procedure 4

N-(4-Benzhydrylphenyl)acetamide (6f)

Under an argon atmosphere, Pd(OAc)₂(3.3 mg, 0.015 mmol, 5 mol%),

ligand [1,1′-biphenyl]-2-yldiphenylphosphane (15 mg, 0.045 mmol,

15 mol%), HCO₂NH₄(23 mg, 0.36 mmol), MeCO₂NH₄(35 mg, 0.45

mmol), benzopheneone N-tosylhydrazone 5a (126 mg, 0.36 mmol),

and Cs₂CO₃(195 mg, 0.6 mmol) were successively added to a flame-

The title compound was prepared following typical procedure 4. After

purification by silica gel column chromatography (eluent: PE–EtOAc,

10:1), the product was isolated as a white solid (70 mg, 78%); mp

163–165 °C.

J

Y. Xia et al.

Paper

Synthesis

IR (film): 1664, 1537, 1512, 732, 699 cm^–1

.

¹³C NMR (100 MHz, CDCl₃): δ = 145.9, 143.0, 134.2, 129.5, 129.4,

129.3, 128.4, 127.6, 126.5, 56.4.

¹H NMR (400 MHz, CDCl₃): δ = 7.48–7.39 (m, 3 H), 7.29–7.18 (m, 6 H),

7.10–7.04 (m, 6 H), 5.50 (s, 1 H), 2.13 (s, 3 H).

¹³C NMR (100 MHz, CDCl₃): δ = 168.3, 143.7, 139.8, 136.0, 129.8,

LRMS (EI): m/z = 278 (M⁺, 61), 243 (71), 201 (15), 165 (100), 152 (9).

HRMS (EI): m/z calcd for C₁₉H₁₅Cl [M]⁺: 278.0862; found: 278.0867.

129.3, 128.2, 126.2, 119.8, 56.2, 24.4.

LRMS (EI): m/z = 301 (M⁺, 100), 259 (40), 224 (15), 182 (64), 165 (30).

1-(3-Benzhydrylphenyl)ethanone (6l)

HRMS (ESI): m/z calcd for C₂₁H₂₀NO [M + H]⁺: 302.1539; found:

302.1549.

The title compound was prepared following typical procedure 4. After

purification by silica gel column chromatography (eluent: PE–EtOAc,

60:1), the product was isolated as a yellow oil (82 mg, 95%).

IR (film): 2924, 1686, 1261, 798, 699 cm^–1

.

{[4-(Trifluoromethyl)phenyl]methylene}dibenzene (6g)^7f

The title compound was prepared following typical procedure 4. After

purification by silica gel column chromatography (eluent: PE), the

product was isolated as a colorless oil (67 mg, 72%).

¹H NMR (400 MHz, CDCl₃): δ = 7.81 (d, J = 7.60 Hz, 1 H), 7.76 (s, 1 H),

7.40–7.36 (m, 1 H), 7.32–7.20 (m, 7 H), 7.10 (d, J = 7.23 Hz, 4 H), 5.61

(s, 1 H), 2.53 (s, 3 H).

¹H NMR (400 MHz, CDCl₃): δ = 7.53 (d, J = 7.6 Hz, 2 H), 7.32–7.22 (m, 8

¹³C NMR (100 MHz, CDCl₃): δ = 198.1, 144.5, 143.1, 137.2, 134.0,

H), 7.10–7.08 (m, 4 H), 5.59 (s, 1 H).

129.3, 129.1, 128.5, 128.4, 126.5, 126.4, 56.6, 26.6.

¹³C NMR (100 MHz, CDCl₃): δ = 147.9, 142.9, 129.7, 129.3, 128.6 (q, J =

31.6 Hz), 128.5, 126.6, 125.2 (q, J = 3.7 Hz), 124.2 (q, J = 271.9 Hz),

56.5.

LRMS (EI): m/z = 286 (M⁺, 100), 271 (32), 243 (76), 165 (75), 152 (12).

HRMS (ESI): m/z calcd for C₂₁H₁₉O [M + H]⁺: 287.1430; found:

287.1438.

[(4-Fluorophenyl)methylene]dibenzene (6h)²⁰

[(3,5-Dimethylphenyl)methylene]dibenzene (6m)

The title compound was prepared following typical procedure 4. After

purification by silica gel column chromatography (eluent: PE), the

product was isolated as a colorless oil (52 mg, 66%).

¹H NMR (400 MHz, CDCl₃): δ = 7.30–7.26 (m, 4 H), 7.23–7.19 (m, 2 H),

The title compound was prepared following typical procedure 4. After

purification by silica gel column chromatography (eluent: PE), the

product was isolated as a white solid (68 mg, 84%); mp 67–69 °C.

IR (film): 1598, 1494, 743, 714, 699 cm^–1

.

7.10–7.04 (m, 6 H), 6.98–6.94 (m, 2 H), 5.52 (s, 1 H).

¹H NMR (400 MHz, CDCl₃): δ = 7.28–7.17 (m, 6 H), 7.12–7.10 (m, 4 H),

6.84 (s, 1 H), 6.73 (s, 2 H), 5.47 (s, 1 H), 2.23 (s, 6 H).

¹³C NMR (100 MHz, CDCl₃): δ = 144.0, 143.7, 137.6, 129.4, 128.2,

127.9, 127.2, 126.1, 56.7, 21.3.

¹³C NMR (100 MHz, CDCl₃): δ = 161.38 (d, J = 244.9 Hz), 143.68,

139.60 (d, J = 3.0 Hz), 130.82 (d, J = 7.9 Hz), 129.32, 128.37, 126.42,

115.05 (d, J = 21.2 Hz), 56.00.

LRMS (EI): m/z = 272 (M⁺, 97), 257 (100), 195 (28), 179 (36), 165 (54).

HRMS (EI): m/z calcd for C₂₁H₂₀[M]⁺: 272.1565; found: 272.1569.

Methyl 4-Benzhydrylbenzoate (6i)²¹

The title compound was prepared following typical procedure 4. After

purification by silica gel column chromatography (eluent: PE–EtOAc,

60:1), the product was isolated as a yellow solid (83 mg, 92%); mp 76–

77 °C.

¹H NMR (400 MHz, CDCl₃): δ = 7.95 (d, J = 8.28 Hz, 2 H), 7.34–7.27 (m,

4 H), 7.24–7.18 (m, 4 H), 7.10–7.08 (m, 4 H), 5.59 (s, 1 H), 3.88 (s, 3 H).

[(2-Methoxyphenyl)methylene]dibenzene (6n)

The title compound was prepared following typical procedure 4. After

purification by silica gel column chromatography (eluent: PE–EtOAc,

100:1), the product was isolated as a white solid (48 mg, 58%); mp

110–111 °C.

¹³C NMR (100 MHz, CDCl₃): δ = 166.9, 149.2, 143.0, 129.5, 129.4,

129.3, 128.4, 128.2, 126.5, 56.7, 51.9.

IR (film): 1489, 1244, 752, 725, 699 cm^–1

.

¹H NMR (400 MHz, CDCl₃): δ = 7.27–7.16 (m, 7 H), 7.09 (d, J = 7.23 Hz,

4 H), 6.87–6.85 (m, 3 H), 5.93 (s, 1 H), 3.70 (s, 3 H).

4-Benzhydrylbenzaldehyde (6j)^7f

¹³C NMR (100 MHz, CDCl₃): δ = 157.0, 143.8, 132.5, 130.3, 129.4,

128.0, 127.4, 125.9, 120.2, 110.6, 55.5, 49.5.

LRMS (EI): m/z = 274 (M⁺, 100), 259 (44), 243 (28), 165 (58), 91 (49).

HRMS (ESI): m/z calcd for C₂₀H₁₈ONa [M + Na]⁺: 297.1250; found:

The title compound was prepared following typical procedure 4. After

purification by silica gel column chromatography (eluent: PE–EtOAc,

60:1), the product was isolated as a yellow oil (68 mg, 83%).

¹H NMR (400 MHz, CDCl₃): δ = 9.98 (s, 1 H), 7.80 (d, J = 8.02 Hz, 2 H),

7.34–7.22 (m, 8 H), 7.10 (d, J = 7.15 Hz, 4 H), 5.62 (s, 1 H).

297.1254.

¹³C NMR (100 MHz, CDCl₃): δ = 191.8, 151.0, 142.7, 134.7, 130.0,

129.7, 129.3, 128.5, 126.7, 56.9.

2-Benzhydrylnaphthalene (6o)^7c

The title compound was prepared following typical procedure 4. After

purification by silica gel column chromatography (eluent: PE), the

product was isolated as a pale yellow solid (65 mg, 74%); mp 77–

78 °C.

¹H NMR (400 MHz, CDCl₃): δ = 7.79–7.68 (m, 3 H), 7.47–7.40 (m, 3 H),

7.32–7.27 (m, 5 H), 7.23–7.14 (m, 6 H), 5.70 (s, 1 H).

[(3-Chlorophenyl)methylene]dibenzene (6k)

The title compound was prepared following typical procedure 4. After

purification by silica gel column chromatography (eluent: PE), the

product was isolated as a colorless oil (63 mg, 76%).

IR (film): 1593, 1474, 780, 763, 741, 699 cm^–1

.

¹H NMR (400 MHz, CDCl₃): δ = 7.28 (t, J = 7.24 Hz, 4 H), 7.23–7.18 (m,

¹³C NMR (100 MHz, CDCl₃): δ = 143.6, 141.4, 133.3, 132.1, 129.5,

4 H), 7.10–7.08 (m, 5 H), 6.99 (m, 1 H), 5.51 (s, 1 H).

128.3, 128.0, 127.8, 127.7, 127.5, 126.3, 125.9, 125.6, 56.9.

K

Y. Xia et al.

Paper

Synthesis

9-Benzhydrylphenanthrene (6p)

3-Benzhydrylquinoline (6t)²³

The title compound was prepared following typical procedure 4. After

purification by silica gel column chromatography (eluent: PE–EtOAc–

CH₂Cl₂, 200:4:1), the product was isolated as a pale yellow solid (78

mg, 76%); mp 168–171 °C.

The title compound was prepared following typical procedure 4. After

purification by silica gel column chromatography (eluent: PE–EtOAc,

20:1), the product was isolated as a colorless oil (58 mg, 66%).

¹H NMR (400 MHz, CDCl₃): δ = 8.79 (d, J = 2.11 Hz, 1 H), 8.09 (d, J =

8.36 Hz, 1 H), 7.71–6.64 (m, 3 H), 7.50–7.46 (m, 1 H), 7.33–7.23 (m, 6

H), 7.16–7.14 (m, 4 H), 5.74 (s, 1 H).

¹³C NMR (100 MHz, CDCl₃): δ = 152.53, 146.76, 142.45, 136.82,

135.23, 129.34, 129.06, 129.02, 128.56, 127.79, 127.66, 126.74,

126.63, 54.39.

IR (film): 1494, 1450, 907, 725, 700 cm^–1

.

¹H NMR (400 MHz, CDCl₃): δ = 8.72 (d, J = 8.22 Hz, 1 H), 8.65 (d, J =

8.24 Hz, 1 H), 8.04 (d, J = 8.22 Hz, 1 H), 7.68–7.48 (m, 5 H), 7.31–7.16

(m, 11 H), 6.26 (s, 1 H).

¹³C NMR (100 MHz, CDCl₃): δ = 143.3, 138.1, 131.3, 131.1, 130.7,

129.8, 129.7, 128.7, 128.6, 128.4, 126.6, 126.5, 126.4, 126.1, 125.1,

123.0, 122.3, 53.4.

4-{[4-(tert-Butyl)phenyl](phenyl)methyl}-1,2-dimethylbenzene

(7a)

LRMS (EI): m/z = 344 (M⁺, 100), 265 (56), 239 (4), 165 (32), 133 (10).

The title compound was prepared following typical procedure 4. After

purification by silica gel column chromatography (eluent: PE), the

product was isolated as a colorless oil (79 mg, 81%).

HRMS (ESI): m/z calcd for C₂₇H₂₀Na [M + Na]⁺: 367.1457; found:

367.1467.

IR (film): 1502, 1493, 811, 732, 700 cm^–1

.

tert-Butyl 5-Benzhydryl-1H-indole-1-carboxylate (6q)

¹H NMR (400 MHz, CDCl₃): δ = 7.28–7.02 (m, 7 H), 7.03 (d, J = 7.92 Hz,

3 H), 6.92 (s, 1 H), 6.83 (d, J = 7.01 Hz, 1 H), 5.43 (s, 1 H), 2.20 (d, J =

11.20 Hz, 6 H), 1.29 (s, 9 H).

¹³C NMR (100 MHz, CDCl₃): δ = 148.7, 144.4, 141.5, 141.0, 136.3,

134.3, 130.7, 129.4, 129.3, 128.9, 128.1, 126.7, 126.0, 125.0, 56.0, 34.3,

31.3, 19.8, 19.3.

The title compound was prepared following typical procedure 4. After

purification by silica gel column chromatography (eluent: PE–CH₂Cl₂,

50:1), the product was isolated as a white solid (94 mg, 82%); mp 99–

101 °C.

IR (film): 1733, 1372, 1162, 730, 700 cm^–1

.

¹H NMR (400 MHz, CDCl₃): δ = 8.03 (d, J = 7.15 Hz, 1 H), 7.56 (d, J =

2.74 Hz, 1 H), 7.29–7.18 (m, 7 H), 7.14–7.10 (m, 5 H), 6.46 (d, J = 3.58

Hz, 1 H), 5.66 (s, 1 H), 1.64 (s, 9 H).

LRMS (EI): m/z = 328 (M⁺, 56), 313 (100), 271 (97), 193 (12), 165 (22).

HRMS (EI): m/z calcd for C₂₅H₂₈[M]⁺: 328.2191; found: 328.2195.

¹³C NMR (100 MHz, CDCl₃): δ = 149.7, 144.2, 138.4, 133.6, 130.6,

129.4, 128.2, 126.2, 126.1, 126.0, 121.5, 114.8, 107.3, 83.5, 56.6, 28.1.

LRMS (EI): m/z = 283 ((M – 100)⁺, 100), 206 (58), 205 (46), 167 (28),

1-(tert-Butyl)-4-[(4-methoxyphenyl)(phenyl)methyl]benzene

(7b)^7c

The title compound was prepared following typical procedure 4. After

purification by silica gel column chromatography (eluent: PE), the

product was isolated as a colorless oil (71 mg, 72%).

¹H NMR (400 MHz, CDCl₃): δ = 7.29–7.10 (m, 7 H), 7.03 (dd, J = 3.13,

152 (10).

HRMS (ESI): m/z calcd for C₂₆H₂₆NO₂[M + H]⁺: 384.1958; found:

384.1966.

8.59 Hz, 4 H), 6.82–6.80 (m, 2 H), 5.46 (s, 1 H), 3.76 (s, 3 H), 1.29 (s, 9

H).

¹³C NMR (100 MHz, CDCl₃): δ = 157.9, 148.8, 144.4, 141.0, 136.3,

5-Benzhydrylbenzo[b]thiophene (6r)

The title compound was prepared following typical procedure 4. After

purification by silica gel column chromatography (eluent: PE), the

product was isolated as a colorless oil (63 mg, 70%).

130.3, 129.3, 128.8, 128.1, 126.0, 125.1, 113.5, 55.5, 55.1, 34.3, 31.3.

IR (film): 1493, 907, 754, 736, 699 cm^–1

.

4-{[(4-(tert-Butyl)phenyl](phenyl)methyl}-1,1′-biphenyl (7c)

¹H NMR (400 MHz, CDCl₃): δ = 7.78 (d, J = 8.36 Hz, 1 H), 7.50 (s, 1 H),

7.40 (d, J = 5.42 Hz, 1 H), 7.31–7.20 (m, 8 H), 7.15–7.14 (m, 4 H), 5.69

(s, 1 H).

¹³C NMR (100 MHz, CDCl₃): δ = 143.9, 140.2, 139.7, 137.7, 129.4,

128.3, 126.5, 126.3, 126.2, 124.1, 123.9, 122.2, 56.6.

LRMS (EI): m/z = 300 (M⁺, 100), 223 (50), 189 (9), 165 (24), 111 (7).

HRMS (EI): m/z calcd for C₂₁H₁₆S [M]⁺: 300.0973; found: 300.0978.

The title compound was prepared following typical procedure 4. After

purification by silica gel column chromatography (eluent: PE), the

product was isolated as a colorless oil (89 mg, 79%).

IR (film): 1487, 909, 824, 763, 733, 699 cm^–1

.

¹H NMR (400 MHz, CDCl₃): δ = 7.55 (d, J = 7.33 Hz, 2 H), 7.49 (d, J =

8.16 Hz, 2 H), 7.39 (t, J = 7.45 Hz, 2 H), 7.31–7.26 (m, 5 H), 7.21–7.15

(m, 5 H), 7.07 (d, J = 8.26 Hz, 2 H), 5.54 (s, 1 H), 1.30 (s, 9 H).

¹³C NMR (100 MHz, CDCl₃): δ = 149.0, 144.0, 143.2, 140.8, 140.6,

139.0, 129.8, 129.4, 128.9, 128.6, 128.2, 127.1, 127.0, 126.9, 126.2,

125.1, 56.1, 34.3, 31.3.

LRMS (EI): m/z = 376 (M⁺, 67), 361 (51), 319 (100), 241 (22), 165 (22).

HRMS (EI): m/z calcd for C₂₉H₂₈[M]⁺: 376.2191; found: 376.2198.

3-Benzhydrylpyridine (6s)²²

The title compound was prepared following typical procedure 4. After

purification by silica gel column chromatography (eluent: PE–EtOAc,

20:1), the product was isolated as a yellow solid (51 mg, 70%); mp 73–

74 °C.

¹H NMR (400 MHz, CDCl₃): δ = 8.47–8.44 (m, 2 H), 7.39 (d, J = 7.88 Hz,

1 H), 7.32–7.28 (m, 4 H), 7.25–7.18 (m, 3 H), 7.10 (d, J = 7.29 Hz, 4 H),

5.55 (s, 1 H).

¹³C NMR (100 MHz, CDCl₃): δ = 150.81, 147.71, 142.63, 139.28,

136.61, 129.23, 128.50, 126.66, 123.17, 54.31.

4,4′-{[4-(tert-Butyl)phenyl]methylene}bis(methylbenzene) (7d)^7c

The title compound was prepared following typical procedure 4. After

purification by silica gel column chromatography (eluent: PE), the

product was isolated as a colorless oil (78 mg, 80%).

L

Y. Xia et al.

Paper

Synthesis

¹H NMR (400 MHz, CDCl₃): δ = 7.27 (d, J = 8.23 Hz, 2 H), 7.08–7.00 (m,

10 H), 5.42 (s, 1 H), 2.30 (s, 6 H), 1.28 (s, 9 H).

¹³C NMR (100 MHz, CDCl₃): δ = 148.7, 141.3, 141.1, 135.5, 129.2,

128.9, 128.8, 125.0, 55.6, 34.3, 31.3, 20.9.

¹H NMR (400 MHz, CDCl₃): δ = 7.22–7.14 (m, 2 H), 7.01 (d, J = 7.48 Hz,

1 H), 6.95 (s, 1 H), 6.90 (d, J = 7.62 Hz, 1 H), 6.84 (s, 1 H), 6.76–6.67 (m,

5 H), 5.39 (s, 1 H), 3.73 (s, 3 H), 2.28 (s, 3 H), 2.24 (s, 6 H).

¹³C NMR (100 MHz, CDCl₃): δ = 159.4, 145.7, 143.7, 143.6, 137.7,

137.6, 130.1, 129.0, 128.0, 127.9, 127.2, 126.9, 126.4, 122.0, 115.6,

111.0, 56.7, 55.0, 21.4, 21.3.

1-(tert-Butyl)-4-[(4-chlorophenyl)(4-ethoxyphenyl)methyl]ben-

zene (7e)

LRMS (EI): m/z = 316 (M⁺, 100), 301 (65), 209 (27), 193 (18), 179 (20).

HRMS (ESI): m/z calcd for C₂₃H₂₅O [M + H]⁺: 317.1900; found:

317.1911.

The title compound was prepared following typical procedure 4. After

purification by silica gel column chromatography (eluent: PE–CH₂Cl₂,

100:1), the product was isolated as a pale yellow oil (66 mg, 58%).

IR (film): 1509, 1489, 1246, 1015, 821 cm^–1

.

3-[(3,4-Dimethylphenyl)(phenyl)methyl]pyridine (7i)

¹H NMR (400 MHz, CDCl₃): δ = 7.29–7.22 (m, 4 H), 7.05–6.98 (m, 6 H),

6.80 (d, J = 8.64 Hz, 2 H), 5.41 (s, 1 H), 3.99 (q, J = 6.99 Hz, 2 H), 1.39 (t,

J = 6.98 Hz, 3 H), 1.29 (s, 9 H).

The title compound was prepared following typical procedure 4. After

purification by silica gel column chromatography (eluent: PE–EtOAc,

20:1), the product was isolated as a pale yellow oil (59 mg, 72%).

¹³C NMR (100 MHz, CDCl₃): δ = 157.4, 149.1, 143.1, 140.5, 135.6,

131.8, 130.6, 130.2, 128.7, 128.3, 125.2, 114.2, 63.3, 54.9, 34.3, 31.3,

14.8.

LRMS (EI): m/z = 378 (M⁺, 79), 363 (43), 321 (100), 267 (27), 181 (19).

HRMS (EI): m/z calcd for C₂₅H₂₇ClO [M]⁺: 378.1750; found: 378.1756.

IR (film): 1494, 1026, 731, 715, 700 cm^–1

.

¹H NMR (400 MHz, CDCl₃): δ = 8.46–8.43 (m, 2 H), 7.40 (d, J = 7.86 Hz,

1 H), 7.31–7.18 (m, 4 H), 7.11–7.05 (m, 3 H), 6.89 (s, 1 H), 6.81 (d, J =

7.63 Hz, 1 H), 5.48 (s, 1 H), 2.23 (s, 3 H), 2.20 (s, 3 H).

¹³C NMR (100 MHz, CDCl₃): δ = 150.77, 147.5, 142.9, 140.0, 139.5,

136.7, 136.6, 134.9, 130.4, 129.7, 129.1, 128.4, 126.6, 126.5, 123.1,

53.9, 19.8, 19.3.

1-{[4-(tert-Butyl)phenyl](phenyl)methyl}-2-chlorobenzene (7f)

LRMS (EI): m/z = 273 (M⁺, 83), 258 (100), 195 (24), 180 (26), 165 (17).

HRMS (ESI): m/z calcd for C₂₀H₂₀N [M + H]⁺: 274.1590; found:

The title compound was prepared following typical procedure 4. After

purification by silica gel column chromatography (eluent: PE), the

product was isolated as a colorless oil (48 mg, 48%).

274.1584.

IR (film): 1468, 1039, 909, 752, 736, 702 cm^–1

.

¹H NMR (400 MHz, CDCl₃): δ = 7.37–7.35 (m, 1 H), 7.30–7.13 (m, 7 H),

7.08 (d, J = 7.25 Hz, 2 H), 7.00–6.96 (m, 3 H), 5.94 (s, 1 H), 1.30 (s, 9 H).

¹³C NMR (100 MHz, CDCl₃): δ = 149.1, 142.7, 141.8, 139.3, 134.5,

131.1, 129.6, 129.4, 129.0, 128.2, 127.6, 126.5, 126.3, 125.1, 52.8, 34.3,

31.3.

3-(Di-p-tolylmethyl)pyridine (7j)

The title compound was prepared following typical procedure 4. After

purification by silica gel column chromatography (eluent: PE–EtOAc,

20:1), the product was isolated as a colorless oil (42 mg, 51%).

IR (film): 1511, 808, 756, 725, 714 cm^–1

.

LRMS (EI): m/z = 334 (M⁺, 41), 319 (100), 277 (92), 165 (61), 128 (21).

HRMS (EI): m/z calcd for C₂₃H₂₃Cl [M]⁺: 334.1488; found: 334.1492.

¹H NMR (400 MHz, CDCl₃): δ = 8.46–8.43 (m, 2 H), 7.40–7.38 (m, 1 H),

7.20–7.17 (m, 1 H), 7.10 (d, J = 7.91 Hz, 4 H), 6.98 (d, J = 8.00 Hz, 4 H),

5.47 (s, 1 H), 2.32 (s, 6 H).

¹³C NMR (100 MHz, CDCl₃): δ = 150.7, 147.5, 139.8, 139.6, 136.5,

136.1, 129.1, 129.0, 123.1, 53.5, 20.9;

LRMS (EI): m/z = 273 (M⁺, 100), 258 (97), 195 (35), 180 (37), 167 (21).

HRMS (ESI): m/z calcd for C₂₀H₂₀N [M + H]⁺: 274.1590; found:

1-{[4-(tert-Butyl)phenyl](3-methoxyphenyl)methyl}-3-methyl-

benzene (7g)

The title compound was prepared following typical procedure 4. After

purification by silica gel column chromatography (eluent: PE), the

product was isolated as a colorless oil (76 mg, 74%).

274.1591.

IR (film): 1488, 1266, 759, 731, 710 cm^–1

.

3-{[4-(tert-Butyl)phenyl](phenyl)methyl}thiophene (7k)^7c

¹H NMR (400 MHz, CDCl₃): δ = 7.28 (d, J = 8.22 Hz, 2 H), 7.22–7.14 (m,

2 H), 7.04–6.90 (m, 5 H), 6.75–6.68 (m, 3 H), 5.43 (s, 1 H), 3.73 (s, 3 H),

2.28 (s, 3 H), 1.29 (s, 9 H).

¹³C NMR (100 MHz, CDCl₃): δ = 159.46, 148.89, 145.88, 143.85, 140.6,

137.7, 130.1, 129.0, 128.9, 128.0, 126.9, 126.4, 125.1, 121.9, 115.6,

111.0, 56.3, 55.0, 34.3, 31.3, 21.4.

The title compound was prepared following typical procedure 4. After

purification by silica gel column chromatography (eluent: PE), the

product was isolated as a colorless oil (39 mg, 42%).

¹H NMR (400 MHz, CDCl₃): δ = 7.30–7.20 (m, 6 H), 7.17–7.15 (m, 2 H),

7.07 (d, J = 8.20 Hz, 2 H), 6.88 (dd, J = 4.85, 0.69 Hz, 1 H), 6.74–6.73 (m,

1 H), 5.47 (s, 1 H), 1.30 (s, 9 H).

LRMS (EI): m/z = 344 (M⁺, 64), 329 (73), 287 (100), 179 (21), 165 (29).

HRMS (ESI): m/z calcd for C₂₅H₂₈ONa [M + Na]⁺: 367.2032; found:

¹³C NMR (100 MHz, CDCl₃): δ = 149.1, 145.1, 144.0, 140.6, 128.9,

128.7, 128.4, 128.2, 126.3, 125.3, 125.1, 122.6, 52.1, 34.3, 31.3.

367.2042.

3-{[4-(tert-Butyl)phenyl](phenyl)methyl}furan (7l)

1-[(3-Methoxyphenyl)(m-tolyl)methyl]-3,5-dimethylbenzene (7h)

The title compound was prepared following typical procedure 4. After

purification by silica gel column chromatography (eluent: PE), the

product was isolated as a colorless oil (26 mg, 30%).

The title compound was prepared following typical procedure 4. After

purification by silica gel column chromatography (eluent: PE), the

product was isolated as a colorless oil (79 mg, 83%).

IR (film): 1024, 874, 775, 729, 702 cm^–1

.

IR (film): 1598, 1487, 758, 728, 700 cm^–1

.

M

Y. Xia et al.

Paper

Synthesis

¹H NMR (400 MHz, CDCl₃): δ = 7.38 (s, 1 H), 7.31–7.20 (m, 8 H), 7.12

(d, J = 8.23 Hz, 2 H), 6.96 (s, 1 H), 6.24 (s, 1 H), 5.24 (s, 1 H), 1.30 (s, 9

H).

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8626.

¹³C NMR (100 MHz, CDCl₃): δ = 149.1, 143.7, 143.0, 140.9, 140.3,

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128.7, 128.4, 128.3, 128.2, 126.3, 125.2, 111.3, 47.6, 34.3, 31.3.

LRMS (EI): m/z = 290 (M⁺, 61), 275 (100), 233 (96), 157 (20), 128 (23).

HRMS (EI): m/z calcd for C₂₁H₂₂O [M]⁺: 290.1671; found: 290.1675.

Acknowledgment

We are grateful to National Basic Research Program of China (973 Pro-

gram, No. 2015CB856600) and Natural Science Foundation of China

(Grant 21472004 and 21332002) for the financial support.

Supporting Information

Supporting information for this article is available online at

http://dx.doi.org/10.1055/s-0036-1588893.

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Article Doi

Synthesis of Di- and Triarylmethanes through Palladium-Catalyzed Reductive Coupling of N -Tosylhydrazones and Aryl Bromides

DOI: 10.1055/s-0036-1588893

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