Cross-Aromaticity in annulated benzene and

analogs

Advisor: Jun Zhu

Reporter:

Yulei.Hao

Date: 2014.3.14

23/4/21 1

Results and Discussion

Futher Work

Background

Computational Methods

23/4/21 2

BackgroundBackground

α

β

Mills–Nixon effect ： Geometric changes of the benzene ring due to annulation by small, strained rings. in terms of the stability of the Kekulé resonance structures, it favor the resonance structure with the double bonds exo to the strained annulated ring.

exoendo

108 1=13

2=1

α=360。

-2βMills, W.H.; Nixon, I.G. J.Chem.Soc. 1930, 2510

23/4/21 3

BackgroundBackground

Coupling of diazo-compounds and Bromination

O2N1.3781.373

1.371

1.367 1.378

1.3911.501

Fuller, F. J.; Valente, J. E. J.Chem.Cryst. 1996, 26, 815.

Mills, W.H.; Nixon, I.G. J.Chem.Soc. 1930, 2510

4

5

6

7

HO

4

5

6

7

HO

N NClN N

OH

N NClH3C

Br2 OHR

R

Br

HO

R

N NH3C

4

5

6

7

HO

N NH3C 4

5 6

7

HO

23/4/21 4

BackgroundBackground

“The field of the cycloproparene chemistry can be aptly regarded as something of a Cinderella area since the simple beginnings have led to a wealth of fascinating and fruitful chemistry far beyond expectation in 1960s.” ----Brian Halton Chem. Rev. 2003, 103, 1327-1369

1.334

1.382

1.390 1.360

[1] Vogel, E.; Grimme, W.; Korte, S. Tetrahedron Lett. 1965, 6, 3625.

COOCH3

COOCH3

TM.1

The synthesis some of cycloproparens:The synthesis some of cycloproparens:

TM.1

23/4/21 5

1.3331.381

1.393

1.3931.518

1.566+

CH2OCH3

Si(CH3)3

CpCo(CO)2

n-octane

CH2OCH3

Si(CH3)3

1. Br2

2. BuLiTM.2

[2]

[3]

[4]

1.375

1.355

1.440

1.448

1.4201.374

1.415

Cl

Cl

KO-t-Bu

dry THFCl Cl TM.3

Ph

Ph1.355

1.3731.382

1.388BuLi Me3SiCl H

SiMe3

BuLi

SiMe3

Ph2COTM.4

TM.2

TM.3

TM.4

23/4/21 6

Computational MethodsComputational Methods

G03 program

OPT ： B3LYP/6-311++G*

NICS: B3LYP/6-311++G*

23/4/21 7

Results and DiscussionResults and Discussion

Figure 1. Monomers of annulated rings in calculation.

Figure 2. Combination of non-π aromatic monomers.

monomer

G=0.86

1 2

3 4

Compounds NICS(0) NICS(1)zz

cyclopropane -42.73 -24.16

3 -47.57 -21.40(-23.53)a

4 -41.96 -18.26(-26.20)

cyclopropene -28.49 -16.17

1 -36.96 1.8

2 -40.57 -27.97(-7.52)

cyclobutane 3.11 5.54

4 -6.74 0.59(3.43)

Table 2. Comparing NICS values(ppm) of 1, 2, 3 and 4 with their monomers. a Numbers in the brackets are NICS(1)zz opposite the dihedral.

23/4/21 8

Results and DiscussionResults and Discussion

(1.498)1.503 1.348(1.334)

(1.367)1.3771.401(1.390)

1.350

1.3951.384

1.3571.361

1.3801.431

5 6 7 8

1.583

1.5231.394

1.386

(1.348)1.356

1.406(1.393)

1.350(1.333)

1.402(1.393)

1.401

1.408

1.400

1.364(1.364)

(1.412)1.415

1.384

9 10 11 12

13 14 15

1.394 1.381

1.5821.581

1.581

1.505(1.498)

1.505(1.504)

1.503(1.512)

Figure 3. Selected bond distances(Å) for 5-15.

1.3281.368(1.375)

1.399 1.356(1.354)

1.337

1.329

1.363(1.360)

1.368

1.329

16 17

18

19

20

21

22

1.406 1.397

1.398

1.359(1.352)

1.401

Figure 4. Selected bond distances(Å) for 16-22.

1.291

1.511

(1.391)1.394

1.431

1.420 1.374

1.415

1.339

1.519

1.573

23/4/21 9

Results and DiscussionResults and Discussion

Compounds aΔR ΔR

5 0.034 16 0.073

6 0.040 17 0.012

7 -0.051

8 -0.027 18 0.069

19 0.069

9 0.016 20 -0.004

10 -0.006 21 0.029

11 -0.020 22 0.072

12 -0.024

13 0.039

14 0.036

15 -0.041

Table 3. ΔR(Å) for compounds 5-22. R defined as the endo distance minus the exo distance. The bond between the two rings is used as the exo bond, and the maximum of the difference is used for the asymmetric compounds.

We can conclude that the bond length in benzene and naphthalene of these compounds change slightly after fused by small strained rings, impling the retained π aromaticity.

23/4/21 10

compounds 3- /4-membered rings 6-membered rings

NICS(0) NICS(1)zz NICS(0) NICS(1)zz

monomers

-28.49 -16.17 -8.02 -29.255 -21.10 -14.48 -7.98 -27.556 -20.91 -6.69 -7.56 -25.857 -18.29 -14.18 -7.79 -26.598 -15.99 -14.72 -11.19 -29.20

monomers

1.43 0.14 -8.41 -29.059 -3.52 3.04 -8.40 -27.7710 2.85 2.80 -8.90 -26.2011 3.30 3.12 -8.65 -26.3912 3.40 3.45 -9.37 -25.23

13 -20.99/ 4.46 -14.20/ 3.11 -8.26 -26.2014 -21.56/ 2.55 -14.34/ 2.11 -8.49 -26.2115 -20.96/4.91 -13.83/ 3.53 -8.89 -25.02

16 -22.29 -13.14 -8.95/ -7.95 -26.88/ -27.8717 -19.85 -13.55 -8.10/ -8.40 -26.60/ -29.0018 -19.51 -12.80 -9.33/ -6.72 -29.56/ -26.5319 -22.12 -13.01 -8.02 -27.5420 -20.65 -13.54 -7.89 -26.4021 -20.19/ -22.49 -13.56/ -25.26 -7.39/ -8.80 -25.26/ -28.6622 -21.93 -12.99 -8.24 -27.81

Table 4. NICS(0) and NICS(1)zz of computed compounds

1.503

1.348

1.377 1.4011.350

1.395

5 6

1.3841.3571.361

1.3801.431

7 8

1.291

1.511 1.394 1.431

1.420 1.374

1.415

1.339

1.519

1.573

1.583

1.5231.394

1.3861.400

9 10

1.394

1.582

1.401

1.408

1.384

11 12

1.3811.581

1.581

1.356

1.406

1.350

1.402

1.364

1.415

13 14 15

1.3281.368

1.399 1.356

1.337

1.329

1.363

1.368

1.329

16 17

18

19

20

21

22

1.406 1.397

1.398

1.359

1.401

The aromaticity of both are The aromaticity of both are not destroyed.not destroyed.

23/4/21 11

Results and DiscussionResults and Discussion

Table 3. Smooth line of NICS(0) vs exo bond distance of compounds 5-22.

NICS(0) -28.49

1.291

1.511

We can conclude that the π-aromaticity in benzene and naphthalene weaken the σ-aromaticity in cyclopropene, and strengthen the σ-antiaromaticity in cyclobutene.

NICS(0) 1.43

1.339

23/4/21 12

G=5.47

13 (Cs)14 (C2v)

G=1.89

6 (D2h) 7 (C2v)

10 (D2h) 11 (C2v)

G=2.57

17 (C2v) 16 (Cs)

G=1.01

18 (C2v)19 (C2v)

20 (D2h) 21 (Cs) 22 (C2h)

G=0.17 G=0.76

G=0.83

G=3.02

Figure 5. The Gibbs Free Energy(in kcal.mol-1) of some compounds to their isomers.

We can conclude that those compounds with higher symmetry are more stable.

Results and DiscussionResults and Discussion

23/4/21 13

Futher WorkFuther Work

……

23/4/21 14

Thank you for listening!

23/4/21 15