Download PDF
Synthesis 2012; 44(20): 3197-3201
DOI: 10.1055/s-0032-1317149
paper
© Georg Thieme Verlag Stuttgart · New York

Synthesis of γ,δ-Unsaturated Selenoamides via the Seleno-Claisen Rearrangement of in situ Generated Allylic Vinyl Selenides from Selenoamides and Allylic Bromides­

Toshiaki Murai*
Department of Chemistry, Faculty of Engineering, Gifu University, Yanagido, Gifu 501-1193, Japan   Fax: +81(58)2932614   Email: mtoshi@gifu-u.ac.jp
,
Tatsuya Ezaka
Department of Chemistry, Faculty of Engineering, Gifu University, Yanagido, Gifu 501-1193, Japan   Fax: +81(58)2932614   Email: mtoshi@gifu-u.ac.jp
,
Shinzi Kato
Department of Chemistry, Faculty of Engineering, Gifu University, Yanagido, Gifu 501-1193, Japan   Fax: +81(58)2932614   Email: mtoshi@gifu-u.ac.jp
› Author Affiliations
Further Information

Publication History

Received: 04 July 2012

Accepted after revision: 31 July 2012

Publication Date:
04 September 2012 (online)

 
 PDF Download Permissions and Reprints All articles of this category


Abstract

The deprotonation of α-monosubstituted selenoamides with LDA followed by allylation gives γ,δ-unsaturated selenoamides in good to high yields. In the initial step, allylation may take place at the selenium atom of lithium eneselenolates to form allylic vinyl selenides, which then undergo seleno-Claisen rearrangement. As allylic bromides, γ,γ-disubstituted compounds such as geranyl and neryl bromides could also be used to give products that incorporated tertiary-quaternary stereogenicity with high efficiency.


#

Key words

seleno-Claisen rearrangement - γ,δ-unsaturated selenoamides - tertiary-quaternary stereogenicity - high stereoselectivity

The Claisen rearrangement is one of the most important and frequently used reactions that leads to γ,δ-unsaturated carbonyl compounds.[ 1 ] The rearrangement of sulfur analogues, that is, the thio-Claisen rearrangement, has also been well documented.[2] [3] In contrast, little is known about the seleno-Claisen rearrangement.[ 4 ] The results reported so far have shown that the seleno-Claisen rearrangement proceeds more readily than ordinary Claisen and thio-Claisen rearrangement. For example, allyl vinyl selenides undergo seleno-Claisen rearrangement at room temperature to generate selenoaldehydes, which are then trapped with cyclopentadiene to form Diels–Alder adducts.[ 4a ] Selenothioic acid ester 1 is treated with allyl bromide in the presence of Et3N to give γ,δ-unsaturated selenothioic acid ester 3 via the seleno-Claisen rearrangement of in situ-generated Se-allylic selenothioacetal 2 (Scheme [1]).[ 5 ]

Zoom Image
Scheme 1

The reaction is complete within two hours below room temperature. This is in marked contrast to the similar reaction of dithioic acid esters, which requires more than two days.[ 6 ] The seleno-Claisen rearrangement may also proceed via the six-membered chair-like transition states similar to Claisen rearrangement.[ 7 ] In the rearrangement, the easiness of the reaction has been discussed based on the aromaticities of the transition states.[ 3f ] DFT calculation has suggested that the aromatic character of the transition states of the sulfur model is more than that of the oxygen model. Although further studies are necessary, a similar notion may be applicable to the selenium case. Additionally, the weakness of the seleniumallylic carbon bond atom may compensate the formation of Se=C bonds.

Among selenocarbonyl compounds, selenoamides, in which an amino group is introduced to the selenocarbonyl carbon atom, are the most readily available.[8] [9] In fact, the generation and reactions of selenium isologues of amide enolates have been studied.[ 10 ] We report here the allylation reaction of lithium eneselenolates derived from selenoamides to give γ,δ-unsaturated selenoamides through seleno­-Claisen rearrangement.

Zoom Image
Scheme 2

Table 1 Synthesis of γ,δ-Unsaturated Selenoamides via the Seleno-Claisen Rearrangementa

Entry

4

6

Conditions

Product, yieldb

1

4a

6a

0 °C, 10 min

8 84%

2

4a

6b

0 °C, 10 min

9 64%

3

4a

6c
(E/Z = 84:16)

0 °C, 10 min

10 88% (83:17)

4

4a

6d

0 °C, then 67 °C, 3 h

11 95% (81:19)

5

4b

6a

0 °C, then 67 °C, 3 h

12 83%

6

4c

6a

0 °C, then 67 °C, 3 h

13 84%

a The reaction was carried out with selenoamide 4 (1 mmol), LDA (1.2 mmol), and allylic bromide 6 (1.2 mmol) in THF (5 mL), unless otherwise noted.

b Isolated yield. The value in parentheses represents the ratio of the two isomers in CDCl3.

Initially, selenoamide 4a was deprotonated with LDA at 0 °C to generate lithium eneselenolate 5a. Allyl bromide (6a) was then added to the reaction mixture, and stirring was continued at 0 °C for 10 minutes (Scheme [2, ]Table [1], entry 1). The usual workup of the reaction mixture gave γ,δ-unsaturated selenoamide 8 as the product. The alkylation of lithium eneselenolates generally takes place on the selenium atom to give vinyl selenides.[ 11 ] Likewise, allylation of 5 may lead to the formation of allyl vinyl selenide 7 as an intermediate, although it could not be detected. The selenide 7 then undergoes seleno-Claisen rearrangement to give the corresponding product 8. A similar reaction with 2-bromoallyl bromide (6b) and crotyl bromide (6c) took place with high efficiency to give selenoamides 9 and 10 in respective yields of 64% and 88% (entries 2 and 3). These results also imply that the seleno-Claisen rearrangement proceeds more readily than the thio-Claisen rearrangement since crotyl vinyl sulfides derived from thioamides required two hours at room temperature or the reflux temperature of THF[ 12 ] to be converted into γ,δ-unsaturated thioamides. In the reaction of 6c, the ratio of the stereoisomers of 6c was retained in the product 10. For the reaction with cyclohex-2-enyl bromide (6d), a higher temperature and longer reaction time were necessary, but the corresponding cyclohexenyl selenoamide 11 was obtained in excellent yields (entry 4). Two diastereomers of 11 were formed in a ratio of 81 to 19, although the stereochemistry of the product was not determined. In this case, 1H NMR spectra of the crude product at room temperature showed that it partially involved the corresponding allylic vinyl selenide 7, although it readily hydrolyzed and could not be isolated.

As selenoamides, γ,δ-unsaturated selenoamide 4b and N,N-diallylselenoamide 4c were also used (entries 5 and 6). The reaction required three hours at the reflux temperature of THF, but gave the corresponding products 12 and 13 in good yields.

Table 2 Synthesis of Selenoamides with a Quaternary Carbon Atom via the Seleno-Claisen Rearrangementa

Entry

4

5

Conditions

Product, yieldb

1

4b

6e

0 °C, then 67 °C, 3 h

14 69%

2

4b

6f

0 °C, then 67 °C, 3 h

15 87% (97:3)

3

6g

0 °C, then 67 °C, 4 h

16 97% (92:8)

4

6f

0 °C, then 67 °C, 3 h

17 63% (95:5)

a The reaction was carried out with selenoamide 4 (1 mmol), LDA (1.2 mmol), and allylic bromide 6 (1.2 mmol) in THF (5 mL).

b Isolated yield. The value in parenthesis represents the ratio of two isomers in CDCl3.

The reaction was then extended to allylic bromides with two alkyl substituents at the terminal alkenyl carbon atom (Table [2]). Initially, prenylation of lithium eneselenolate 5 derived from 4b with 6e was carried out, and a similar seleno-Claisen rearrangement proceeded smoothly to give the corresponding product 14, in which a quaternary carbon atom was constructed at the carbon atom β to the selenocarbonyl group with high efficiency (Table [2], entry 1). Geranyl bromide (6f) and neryl bromide (6g) also participated in the allylation reaction (entries 2–4). The longer alkyl chains in 6f and 6g did not influence the efficiency of the reaction, and seleno-Claisen rearrangement proceeded in a highly stereoselective manner to give the corresponding products 16 and 17.[ 13 ]

In summary, we have demonstrated an allylation reaction of lithium eneselenolates derived from selenoamides. The initial allylation may take place at the selenium atom to form allylic vinyl selenides, which then undergo seleno-Claisen rearrangement to give the allylated products at the α-position to the selenocarbonyl group. The rearrangement proceeded highly efficiently even when the quaternary carbon atom was formed. With this method, the construction of tertiary-quaternary carbon stereogen­icity[ 14 ] has been achieved. The versatility of selenoamides and their unique reaction modes in carbon–carbon bond-forming reactions[ 15 ] have proven the synthetic utility of the present reactions. Further development of selenoamide-based synthetic methods is currently being studied.

All reactions were carried out under an argon atmosphere. THF was distilled from sodium benzophenone ketyl prior to use. Melting points were determined on a Yanagimoto melting point apparatus without correction. 1H NMR (400 MHz) and 13C NMR (100 MHz) were recorded on a JEOL α-400 MHz spectrometer using TMS as an internal standard for 1H NMR and CDCl3 for 13C NMR. Mass spectra were recorded on a Shimadzu GCMS QP1000 (EI/CI, model) mass spectrometer. Elemental analyses were carried out at the Elemental Analyses Center of Kyoto University.


#

γ,δ-Unsaturated Selenoamides via Seleno-Claisen Rearrangement; 1-(2,3-Dimethyl-1-selenoxopent-4-enyl)pyrrolidine (10); Typical Procedure

To a THF solution (5 mL) of LDA, generated from i-Pr2NH (0.34 mL, 2.4 mmol) and n-BuLi (1.6 M hexane solution, 1.50 mL, 2.4 mmol) was added selenoamide 4a (0.380 g, 2.0 mmol) at 0 °C, and the mixture was stirred for 10 min at this temperature. Crotyl bromide (6c; 0.25 mL, 2.4 mmol) was then added, and the mixture was stirred for 10 min. The mixture was poured into brine (5 mL), and extracted with Et2O (3 × 5 mL). The combined organic layers were dried (Na2SO4) and concentrated. The residue was purified by column chromatography on silica gel (hexane–CH2Cl2, 3:1) to give an 87:13 mixture of anti-10/syn-10 (0.428 g, 88%) as a yellow oil. The diastereomeric products were distinguishable by their 1H and 13C NMR spectra. The relative stereochemistry of the isomers was determined by comparison of their 1H NMR spectra with those of similar γ,δ-unsaturated carbonyl compounds.[ 16 ]

1H NMR (CDCl3): δ (anti-10) = 0.95 (d, J = 6.6 Hz, 3 H), 1.20 (d, J = 6.6 Hz, 3 H), 1.93–2.22 (m, 4 H), 2.64 (dq, J = 6.6, 9.8 Hz, 1 H), 2.73–2.89 (m, 1 H), 3.45–3.67 (m, 2 H), 3.86–4.03 (m, 2 H), 5.05 (ddd, J = 0.5, 1.8, 10.2 Hz, 1 H), 5.13 (ddd, J = 0.9, 1.8, 17.1 Hz, 1 H), 5.73 (ddd, J = 8.8, 10.2, 17.1 Hz, 1 H); δ (syn-10) = 1.13 (d, J = 6.8 Hz, 3 H), 1.28 (d, J = 6.4 Hz, 3 H), 1.93–2.22 (m, 4 H), 2.72 (dq, J = 6.4, 9.4 Hz, 1 H), 2.73–2.89 (m, 1 H), 3.45–3.67 (m, 2 H), 3.86–4.03 (m, 2 H), 4.93 (ddd, J = 0.9, 1.8, 10.4 Hz, 1 H), 5.06 (ddd, J = 1.2, 1.8, 17.3 Hz, 1 H), 5.75 (ddd, J = 6.8, 10.4, 17.3 Hz, 1 H).

13C NMR (CDCl3): δ (anti-10) = 19.1, 20.4, 23.7, 26.0, 45.5, 51.6, 52.1, 57.7, 115.2, 141.4, 210.5; δ (syn-10) = 15.9, 19.4, 23.7, 25.9, 43.3, 51.7, 52.4, 57.5, 114.0, 141.8, 210.1.

EIMS: m/z = 245 [M+].

Anal. Calcd for C11H19NSe: C, 54.10; H, 7.84. Found: C, 54.37; H, 7.78.


#

1-(2-Allyl-1-selenoxohexyl)pyrrolidine (8)

Yield: 386 mg (84%); yellow oil.

1H NMR (CDCl3): δ = 1.25 (d, J = 6.8 Hz, 3 H), 1.95–2.05 (m, 2 H), 2.07–2.18 (m, 2 H), 2.33 (dt, J = 7.2, 13.9 Hz, 1 H), 2.62 (dt, J = 6.7, 13.9 Hz, 1 H), 2.94 (sext, J = 6.8 Hz, 1 H), 3.50–3.66 (m, 2 H), 3.84–3.98 (m, 2 H), 4.97–5.04 (m, 1 H), 5.04–5.13 (m, 1 H), 5.77 (dddd, J = 6.7, 7.2, 10.3, 16.9 Hz, 1 H).

13C NMR (CDCl3): δ = 21.0, 23.7, 26.0, 42.2, 46.9, 51.3, 57.7, 116.8, 135.8, 210.4 (C=Se).

EIMS: m/z = 231 [M+].

Anal. Calcd for C10H17NSe: C, 52.17; H, 7.44. Found: C, 52.29; H, 7.53.


#

1-(4-Bromo-2-methyl-1-selenoxopent-4-enyl)pyrrolidine (9)

Yield: 396 mg (64%); yellow solid; mp 47.5–48.5 °C.

1H NMR (CDCl3): δ = 1.25 (d, J = 6.7 Hz, 3 H), 1.95–2.08 (m, 2 H), 2.09–2.22 (m, 2 H), 2.67 (dd, J = 6.8, 14.1 Hz, 1 H), 3.03 (dd, J = 6.7, 14.1 Hz, 1 H), 3.32 (sext, J = 6.7 Hz, 1 H), 3.55–3.64 (m, 1 H), 3.71–3.80 (m, 1 H), 3.89 (t, J = 7.1 Hz, 2 H), 5.43 (d, J = 1.0 Hz, 1 H), 5.73 (d, J = 1.0 Hz, 1 H).

13C NMR (CDCl3): δ = 20.4, 23.7, 26.1, 44.8, 49.4, 51.4, 57.8, 119.7, 131.1, 208.8 (C=Se).

EIMS: m/z = 230 [M+ – Br].

Anal. Calcd for C10H16BrNSe: C, 38.86; H, 5.22. Found: C, 38.84; H, 5.14.


#

1-[2-(Cyclohex-3-enyl)-1-selenoxopropyl]pyrrolidine (11)

Yield: 514 mg (95%); yellow solid; mp 63–67 °C.

1H NMR (CDCl3): δ (major diastereomer) = 1.26 (d, J = 6.1 Hz, 3 H), 1.33–1.46 (m, 1 H), 1.48–1.67 (m, 1 H), 1.67–1.78 (m, 1 H), 1.88–2.20 (m, 7 H), 2.65–2.78 (m, 2 H), 3.45–3.68 (m, 2 H), 3.86–4.01 (m, 2 H), 5.46 (dd, J = 1.2, 10.2 Hz, 1 H), 5.63–5.72 (m, 1 H); δ (minor diastereomer) = 1.05–1.15 (m, 1 H), 1.28 (d, J = 6.1 Hz, 3 H), 1.48–1.67 (m, 1 H), 1.78–1.87 (m, 1 H), 1.88–2.20 (m, 7 H), 2.65–2.78 (m, 2 H), 3.45–3.68 (m, 2 H), 3.86–4.01 (m, 2 H), 5.72–5.80 (m, 1 H), 5.89 (dd, J = 1.8, 10.4 Hz, 1 H).

13C NMR (CDCl3): δ (major diastereomer) = 19.4, 21.1, 23.7, 25.1, 25.9, 26.1, 41.7, 51.7, 51.9, 57.5, 128.1, 129.4, 210.5; δ (minor diastereomer) = 19.1, 21.0, 23.7, 25.2, 26.0, 27.5, 41.5, 51.57, 51.61, 57.7, 128.1, 128.5, 210.8 (C=Se).

EIMS: m/z = 271 [M+].

Anal. Calcd for C13H21NSe: C, 57.77; H, 7.83. Found: C, 57.56; H, 7.97.


#

1-(2-Allyl-1-selenoxopent-4-enyl)pyrrolidine (12)

Yield: 425 mg (83%); yellow oil.

1H NMR (CDCl3): δ = 1.99 (quint, J = 6.9 Hz, 2 H), 2.09 (quint, J = 6.8 Hz, 2 H), 2.34–2.42 (m, 2 H), 2.62–2.72 (m, 2 H), 2.92–3.02 (m, 1 H), 3.57 (t, J = 7.0 Hz, 2 H), 3.91 (t, J = 7.1 Hz, 2 H), 5.00 (ddt, J = 1.0, 2.0, 10.2 Hz, 2 H), 5.10 (ddt, J = 1.5, 2.0, 17.1 Hz, 2 H), 5.75 (dddd, J = 6.3, 7.9, 10.0, 16.7 Hz, 2 H).

13C NMR (CDCl3): δ = 23.7, 26.0, 40.7, 51.9, 52.8, 57.7, 117.0, 135.5, 208.5 (C=Se).

EIMS: m/z = 257 [M+].

Anal. Calcd for C12H19NSe: C, 56.25; H, 7.47. Found: C, 56.10; H, 7.50.


#

N,N-Diallyl-2-allylpent-4-eneselenoamide (13)

Yield: 475 mg (84%); yellow oil.

1H NMR (CDCl3): δ = 2.38–2.47 (m, 2 H), 2.58–2.67 (m, 2 H), 2.99 (tt, J = 6.0, 8.0 Hz, 1 H), 4.16–4.22 (m, 2 H), 4.79 (d, J = 5.9 Hz, 2 H), 4.98–5.31 (m, 8 H), 5.66–5.81 (m, 3 H), 5.93 (ddt, J = 5.9, 10.3, 17.0 Hz, 1 H).

13C NMR (CDCl3): δ = 41.4, 50.6, 53.4, 60.0, 117.4, 118.4, 118.9, 130.5, 130.7, 135.4, 215.4 (C=Se).

EIMS: m/z = 283 [M+].

Anal. Calcd for C14H21NSe: C, 59.57; H, 7.50. Found: C, 59.56; H, 7.46.


#

1-(2-Allyl-3,3-dimethyl-1-selenoxopent-4-enyl)pyrrolidine (14)

Yield: 393 mg (69%); yellow solid; mp 43–45 °C.

1H NMR (CDCl3): δ = 1.16 (s, 3 H), 1.23 (s, 3 H), 1.92–2.14 (m, 4 H), 2.23–2.32 (m, 1 H), 2.90 (dd, J = 2.3, 11.3 Hz, 1 H), 2.95–3.05 (m, 1 H), 3.44–3.53 (m, 1 H), 3.63 (dt, J = 6.2, 12.4 Hz, 1 H), 3.85 (dt, J = 7.1, 14.1 Hz, 1 H), 3.99 (dt, J = 7.0, 14.0 Hz, 1 H), 4.90–5.10 (m, 4 H), 5.66 (dddd, J = 6.2, 7.6, 10.0, 13.9 Hz, 1 H), 6.06 (dd, J = 10.7, 17.3 Hz, 1 H).

13C NMR (CDCl3): δ = 23.9, 26.1, 24.3, 25.2, 37.1, 39.9, 52.6, 57.9, 60.6, 111.6, 116.4, 137.0, 146.8, 206.3 (C=Se).

EIMS: m/z = 285 [M+].

Anal. Calcd for C14H23NSe: C, 59.15; H, 8.15. Found: C, 59.10; H, 8.28.


#

anti-1-(2,3,7-Trimethyl-1-selenoxo-3-vinyloct-6-enyl)pyrrolidine (15)

Yield: 569 mg (87%); yellow oil.

The stereochemistry of 15 was tentatively determined by PNOESY spectroscopy.

1H NMR (CDCl3): δ = 1.21 (s, 3 H), 1.27 (d, J = 6.8 Hz, 3 H), 1.40–1.49 (m, 1 H), 1.56 (d, J = 0.5 Hz, 3 H), 1.66 (d, J = 1.0 Hz, 3 H), 1.68–1.88 (m, 3 H), 1.94–2.03 (m, 2 H), 2.04–2.13 (m, 2 H), 3.01 (q, J = 6.8 Hz, 1 H), 3.44–3.53 (m, 1 H), 3.64–3.74 (m, 1 H), 3.83–4.02 (m, 2 H), 5.00 (dd, J = 1.4, 17.5 Hz, 1 H), 5.03–5.09 (m, 1 H), 5.10 (dd, J = 1.4, 10.9 Hz, 1 H), 5.82 (dd, J = 10.9, 17.5 Hz, 1 H).

13C NMR (CDCl3): δ = 17.6, 17.8, 19.0, 22.8, 23.8, 25.6, 26.1, 36.7, 43.4, 52.4, 54.5, 58.0, 113.4, 124.8, 131.0, 145.4, 208.0 (C=Se).

EIMS: m/z = 327 [M+].

Anal. Calcd for C17H29NSe: C, 62.56; H, 8.96. Found: C, 62.64; H, 9.13.


#

syn-1-(2,3,7-Trimethyl-1-selenoxo-3-vinyloct-6-enyl)pyrrolidine (16)

Yield: 634 mg (97%); yellow oil.

The stereochemistry of 16 was tentatively determined by comparison of its 1H and 13C NMR spectra with those of 15.

1H NMR (CDCl3): δ = 1.21 (s, 3 H), 1.27 (d, J = 6.8 Hz, 3 H), 1.41–1.51 (m, 1 H), 1.58 (s, 3 H), 1.58–1.65 (m, 1 H), 1.67 (s, 3 H), 1.79–1.94 (m, 2 H), 1.98 (quint, J = 6.8 Hz, 2 H), 2.10 (quint, J = 6.8 Hz, 2 H), 3.03 (q, J = 6.8 Hz, 1 H), 3.46–3.56 (m, 1 H), 3.61–3.71 (m, 1 H), 3.79–3.89 (m, 1 H), 3.89–4.00 (m, 1 H), 4.95 (dd, J = 1.3, 17.6 Hz, 1 H), 5.05–5.10 (m, 1 H), 5.07 (dd, J = 1.3, 10.8 Hz, 1 H), 6.13 (dd, J = 10.8, 17.6 Hz, 1 H).

13C NMR (CDCl3): δ = 17.6, 17.8, 19.9, 22.8, 23.8, 25.6, 26.1, 38.6, 43.2, 52.4, 54.3, 57.9, 113.1, 124.6, 131.1, 143.5, 208.1 (C=Se).

EIMS: m/z = 327 [M+].

Anal. Calcd for C17H29NSe: C, 62.56; H, 8.96. Found: C, 62.64; H, 8.91.


#

1-(2-Allyl-3,7-dimethyl-3-vinyloct-6-enyl)pyrrolidine (17)

Yield: 445 mg (63%); yellow oil.

1H NMR (CDCl3): δ = 1.24 (s, 3 H), 1.42–1.75 (m, 2 H), 1.56 (s, 3 H), 1.66 (s, 3 H), 1.75–1.90 (m, 2 H), 1.90–2.12 (m, 4 H), 2.24–2.34 (m, 1 H), 2.92 (dd, J = 1.7, 11.5 Hz, 1 H), 2.94–3.04 (m, 1 H), 3.48 (dt, J = 6.3, 12.7 Hz, 1 H), 3.64 (dt, J = 6.3, 12.6 Hz, 1 H), 3.87 (dt, J = 7.1, 14.2 Hz, 1 H), 3.98 (dt, J = 7.1, 14.1 Hz, 1 H), 4.90–5.16 (m, 5 H), 5.63 (dddd, J = 6.1, 7.7, 10.0, 16.5 Hz, 1 H), 5.83 (dd, J = 10.9, 17.4 Hz, 1 H).

13C NMR (CDCl3): δ = 17.6, 18.9, 25.6, 22.8, 23.8, 26.1, 36.9, 37.1, 43.6, 52.5, 57.9, 61.0, 113.6, 116.4, 124.7, 136.8, 145.5, 151.1, 206.1 (C=Se).

EIMS: m/z = 353 [M+].

Anal. Calcd for C19H31NSe: C, 64.75; H, 8.87. Found: C, 64.71; H, 8.76.


#
#

Acknowledgment

This work was supported by the Grants-in-Aid for Scientific Research on Innovative Areas ‘Organic Synthesis based on Reaction Integration. Development of New Methods and Creation of New Substances’ (No, 2105) and by the Collaborative Research Program of Institute for Chemical Research, Kyoto University (grant # 2012-10).



   Permissions and Reprints All articles of this category
Zoom Image
Scheme 1
Zoom Image
Scheme 2