3 Substituted alkenes synthesis mechanistic views II

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alkenylboronic acids which can be synthesized by reaction of terminal acetylenes with catecholborane and subsequent hydrolysis [4]. Boronic acids react with ...
REVISTA BOLIVIANA DE QUÍMICA Bolivian Journal of Chemistry Received 03 23 2015

Accepted 04 15 2015 Bravo et Vila

Vol. 32, No.1, pp. 15-23, Ene./Abr. 2015 31(2) 15-23, Jan./Apr. 2015 Published 04 30 2015 .

MECHANISTIC VIEWS OF STEREOSELECTIVE SYNTHESIS OF TRIAND TETRA-SUBSTITUTED ALKENES, PART II; THE ORGANIC CHEMISTRY NOTEBOOK SERIES, A DIDACTICAL APPROACH, Nº 4 José A. Bravo*, José L. Vila Department of Chemistry, Laboratorio de Síntesis y Hemisíntesis, Instituto de Investigaciones en Productos Naturales IIPN, Universidad Mayor de San Andrés UMSA, P.O. Box 303, Calle Andrés Bello s/n, Ciudad Universitaria Cota Cota, Tel. 59122792238, La Paz, Bolivia

Keywords: Organic Chemistry, Stereoselective synthesis, Alkenes, Addition reaction, Mechanisms of Reactions. ABSTRACT This is the complementing part of the previously published: “Mechanistic views of stereoselective synthesis of triand tetra-substituted alkenes, part I; The Organic Chemistry Notebook Series, a Didactical Approach, Nº 3”. As underlined in three previous papers the presentation of synthesis works in a verbal and graphical succinct manner, needs a didactical approach. Isomerically pure tri- and tetra-substituted alkenes are difficult to obtain as shown in several publications. We used a series of reactions to synthesize tri- and tetra-substituted alkenes as reviewed by W. Carruthers, and we have proposed didactical and mechanistic views for the reviewed reactions. These two latest approaches are included in the synthetic methods reviewed by W. Carruthers with respect to the “Formation of carbon-carbon double bonds”. Spanish title: Vistas mecanísticas de síntesis estereoselectivas de alquenos tri y tetrasubstituidos, Parte II, Serie: El cuaderno de notas de química orgánica, un enfoque didáctico, Nº4.

*Corresponding author: [email protected] ANALYSIS AND MECHANISTIC PROPOSALS As academics we are concerned with the didactical importance of covering the needs of debutant students in organic synthesis. This is the fourth study in: “The Organic Chemistry Notebook Series, a Didactical Approach” [1-3]. The present article is the completion of the analytical and didactical approach to stereoselective synthesis of tri- and tetrasubstituted alkenes as reviewed by W. Carruthers [4], and illustrated mechanistically by J. Bravo and J. Vila [3]. Triand tetra-substituted alkenes are difficult to obtain. Authors [4] mentioned other methods signaled as useful for the stereospecific synthesis of alkenes starting with alkynes. The procedure starts with alkenylalanes and alkenylboranes. The first are obtained by hydroalumination of alkynes with e.g. diisobutylaluminium hydride. The addition is cis type, giving rise to Z-alkenylalanes. The Z-alkenylalanes react with halogens with retention of configuration to afford alkenyl halides. The halogen atoms can be replaced by alkyl groups by means of reacting with an organocopper reagent. Iodination of the alane obtained from reaction of 1-hexyne with diisobutylaluminium hydride makes possible the (E)-1-iodo-1-hexene. 3-hexyne gives (E)-3-iodo-3-hexene [4]. See Figure 1 for the reactions reviewed by W. Carruthers [4]. C4H9

C

C H

(iso-C4H9 )2AlH

H C C

C7H16

C4H9

H

Al(iso C4H9)2 (1) I , THF, -50oC 2 (2) H3O

H

I C C

+

C4H9

H (74%)

C2H5

C

C C2H5

C2H5

(iso-C4H9 )2AlH C2H5 C C C7H16

H

o

(1) I2, THF, -50 C

+ Al(iso C4H9)2 (2) H3O

C2H5

C2H5 C C H

I (72%)

Figure 1. Obtention of alkenyl halides via alkenylalanes [(E)-1-iodo-1-hexene and (E)-3-iodo-3-hexene; reviewed by W. Carruthers [4] Downloadable from: Revista Boliviana

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REVISTA BOLIVIANA DE QUÍMICA Bolivian Journal of Chemistry Received 03 23 2015

Vol. 32, No.1, pp. 15-23, Ene./Abr. 2015 31(2) 15-23, Jan./Apr. 2015 Published 04 30 2015

Accepted 04 15 2015 Bravo et Vila

.

Figure 2 shows the mechanistic proposal for these reactions. (iso-C4H9 )2Al

(iso-C4H9 )2Al+

H

.. O ..

(iso-C4H9 )2Al+ + H C

C C:-

C H

H

(iso-But)2Al

+ + I + I

H

C:-

H H

H

1-hexyne optionally: I

H

O+ (iso-But)2Al-

.. O+

1st

2nd

I+ H

-

+ I Al(i-But)2

+ H

+

.. O+

.. O+

-

+ I Al(i-But)2

Al-(i-But)2

H I

(E)-1-iodo-1-hexene .. O .. (iso-C4H9 )2Al

(iso-C4H9 )2Al

O+

H C

+ I2

+

H

C

(iso-But)2Al-

(iso-But)2Al

C:-

C

H

3-hexyne

H

I+ 2nd

H

I +

1st

.. O+

.. O+

-

+ I Al(i-But)2

Al-(i-But)2 I

(E)-3-iodo-3-hexene

Figure 2. Synthesis of (E)-1-iodo-1-hexene and (E)-3-iodo-3-hexene, mechanistic views

Alternatively, Z- and E-1-halogenoalkenes can be obtained from terminal acetylenes by means of the use of Ealkenylboronic acids which can be synthesized by reaction of terminal acetylenes with catecholborane and subsequent hydrolysis [4]. Boronic acids react with sodium hydroxide to replace the boronic acid group by iodine to afford E-1-iodoalkene; retention of configuration occurs [4]. If the reaction is carried out with bromine and base, the substitution result implies inversion; Z-1-bromoalkene is obtained [4]. In both reactions, the stereoselectivity is high; for example, 1-octyne gave (Z)-1-bromo-1-octene (85% yield, 99% stereoselectivity), and 1-hexyne gave (E)-1-iodo1-hexene [4]. Figure 3 and 4 show the global reactions and the mechanistic approach, respectively. O BH

1) C4H9

C

C4H9

O

C H 2)

H C C

H3O+

H

B OH

C6H13

C

BH

C6H13

O

C H 2)

H C

H3O+

H

C B

H C

(2) NaOH

C

H I (89%; more than 99% E)

HO

O

1)

C4H9

(1) I2

(1) Br2, CH2Cl2

C6H13

Br C

(2) NaOCH3

C

H

CH3OH

H

(85%; 99% Z) R

H C

H

C B

Br2

NaOCH3

R

H

Br C

H

rotate 120o

C B Br

R

Br

Br

C C H H B

CH3O-

R

Br C C

H

H

Figure 3. Obtention of (E)-1-halogenoalkenes from terminal acetylenes via E-alkenylboronic acids. Inversion of configuration during bromination. Reviewed by W. Carruthers [4]

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REVISTA BOLIVIANA DE QUÍMICA Bolivian Journal of Chemistry Received 03 23 2015

Vol. 32, No.1, pp. 15-23, Ene./Abr. 2015 31(2) 15-23, Jan./Apr. 2015 Published 04 30 2015

Accepted 04 15 2015 Bravo et Vila

.

Inversion of configuration in brominating is explained by the trans-addition of Br2 to the double bond and ulterior trans-elimination of boron and bromine due to NaOCH3 ([4], Figure 3). O H B

O +

C

C

H

H O O

C C _ B

H

H C

H3 O+

C O

B O

H 1-hexyne H

H

C

C

+

H

H2O

H

H C

C

O

B

C

C

H

O

B

O

H

H

H2O

H O+H 2

O

O

B O+

H

OH

H2O

H

H

C

C

H

O

B

Na+OH-

OH + H+ OH

O H B

OH

H

H

C C

Na+

O

C6H13

I-

+ + Na + B(OH)3 +

C6H13

C

C H 1-octyne

I-

+ I+

H O O

+ C C _ B

OH I

H

_ C C:

H

+ C C _ OH Na B OH HO

H

O

H

H

H

Br+ H

C6H13

C

C O

B

H

C6H13 +

-

Br Br

Br+

H

C6H13

Br

B

H

O

O

H C C-:

C C

B

H

O

O

O

BrC6H13

Br

H C C

Br

o

rotate 120

C C B H Br

H O

B

H

Br

C6H13

Br

C6H13

C6H13

Br

Br

Br O B

C C

C C H H B

H

H

Na+O-CH3

O

O

Na+

Na+ C6H13

Br

_ Br

H

O

C6H13

B

C C H

Br

..

C C O

OCH3

H

Br H

+

O

C C

CH3O B O

Br

C6H13

O

_

H

H

+

NaBr +

BOCH3 O

Figure 4. Obtention of (E)-1-halogenoalkenes from terminal acetylenes via E-alkenylboronic acids. Inversion of configuration during bromination, mechanistic view

On other topics, the reviewer mentions αβ-unsaturated carboxylic acids obtained from aluminates that at their turn were afforded by alkenylalanes after reaction with methyl-lithium. In the same manner, paraformaldehyde and other similar compounds give rise to allylic alcohols [4,5]. The difference between this reaction and the one previously exposed regarding hydroalumination of disubstituted acetylenes with lithium hydridodiisobutylmethylaluminate obtained from diisobutylalumimium hydride and methyl-lithium, is the trans addition to the alkyne multiple bond [4,5]. Carbonation gives αβ-unsaturated carboxylic acids. The reaction with paraformaldehyde/acetaldehyde gives allylic alcohols; iodine, alkenyl iodides. All these derivatives are isomeric with compounds obtained using diisobutylalumimium hydride discussed previously [4,6]. Both isomers cis and trans αmethylcrotonic acids were obtained from 2-butyne [4,6]. Figure 5 shows the reaction sequences; Figure 6 the applicable theoretical mechanistic proposals. ‘In all these reactions the isobutyl groups of the hydroaluminating agent Downloadable from: Revista Boliviana

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Accepted 04 15 2015 Bravo et Vila

.

are converted into isobutane in the hydrolysis step, and do not interfere with the isolation of the products’ (W. Carruthers [4]). See Figure 6. CH3

C

CH3

(iso-C4H9 )2AlH

C CH3

CH3

o

CH3Li, ether, -30 C

C C H

2-butyne

CH3

CH3 C C

CH3

CH3 C C

Li

Al(iso-C4H9)2

H

Al(iso-C4H9)2

CO2, H3O+ +

H

CO2H (76%)

CH3

(1) paraformaldehyde CO2, H3O+

(2) H3O+

CH3

H

C C

CH3

C C CH3

CH3

H

CO2H (72%)

CH2OH (68%)

Figure 5. Obtaining of αβ-unsaturated carboxylic acids and allylic alcohol from aluminates; reviewed by W. Carruthers [4] (iso-C4H9)2Al+

C

CH3

C

CH3

CH3

C C:-

H (iso-C4H9)2Al

H 2-butyne CH3

H

Al(iso-C4H9)2

CH3

CH3

_ C C:

H

(iso-C4H9 )2Al

O

Li+

H

(iso-C4H9)2Al

C

Al(iso-C4H9)2

CH3 C C

O

C

O

CH3 C C

O

O-

CH3

H

H3O+ CH3

C

trans-crotonic acid + LiOH + Al(iso-C4H9)2 +H+ CH3

Li+

Li+ H

CH3

C C:-

Li+ CH3-

CH3

H C

C C

CH3

Al(iso-C4H9)2

CH3

CH3

CH3 C_ Al(iso-C4H9)2

2-butyne

CH3

Li+ H

H

CH3

_ C C:

C

CH3

CH3

C

H

solvolysis HO O H CH2 H n n paraformaldehyde CH2

O

H2O

Al CH3

C CH3

H O

n-1

CH3 OH

C

H

H

O CH2 +

C4H9 Al

-

O+H2

C4H9

C4H9 Al

+

Al(iso-C4H9)2 + LiOH + CH3

CH2OCH2

HO

formaldehyde

H O

-

C4H9

C4H9 Al CH3

H+

Solvolysis

n-1 n-1 O=CH2

n-1

formaldehyde

paraformaldehyde

OH +

CH3

CH3

OH

H

H3O+

H O CH2++ -O CH2OCH2

O+H2 C4H9 Al C4H9 + CH3

CH3 O- Li+ H

Al(iso-C4H9)2 CH3 HO

O

HO

(iso-C4H9 )2Al+ H

C

C

CH3

H

CH3

_ C C:

Al(iso-C4H9)2

H

Li+ CH3-

CH3 C

2-butyne

CH3

(iso-C4H9 )2Al

H

CH3

C C:-

CH3

CH3

H3O+

O

+

2-butyne Li+ H

CH3 C C _ O

H

CH3

cis-crotonic acid + LiOH + Al(iso-C4H9)2 +H+ CH3 Li+ CH3 C C_ Al(iso-C4H9)2

CH3

O

H

C

HO

CH3

C

O

CH3

H

Al(iso-C4H9)2

H

Al(iso-C4H9)2 CH3

+

CH3

H

CH3 C

Li+

CH3 C C _ Al(iso-C4H9)2

C C

CH3 C

H

Li+

CH3

Li+ CH3-

CH3 C C

OH +

C4H10 isobutane

H2O

C4H9 Al-

O+H2

CH3

OH O+H2

+ C 4H 9

Al CH3

OH

+ C4H10 isobutane

Figure 6. Obtaining of αβ-unsaturated carboxylic acids and allylic alcohol from aluminates; mechanistic views Downloadable from: Revista Boliviana

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Vol. 32, No.1, pp. 15-23, Ene./Abr. 2015 31(2) 15-23, Jan./Apr. 2015 Published 04 30 2015

Accepted 04 15 2015 Bravo et Vila

.

In contrast with alkenylalanes, alkenylboranes (obtainable from hydroboration of alkynes) exhibit a different comportment. Under iodination, no iodide is produced, instead, the stereospecific transfer of one alkyl group from boron to its vicinal carbon occurs. This provides an alternative stereospecific synthesis of substituted alkenes [4]. In this way, iodine and sodium hydroxide added to the alkenylborane obtained after hydroboration of 1-hexyne with dicyclohexylborane, conducts to (Z)-1-cyclohexyl-1-hexene (75% yield). See Figure 7 for the reaction reviewed by W. Carruthers [4]. Figure 8 shows the corresponding mechanistic view. C6H11 C6H11 C4H9

C

C

H

(C6H11)2BH H

I2, NaOH

C4H9

H

C4H9

C4H9

C

C I+

I

H

C

B

H

C6H11

H

B C6H11 C

C C

1-hexyne

H

B(C6H11)2

I-

I

C4H9

=

B H C6H11

C

C

I

H

I

H C

H C6H11

C4H9

C C6H11

(75% Z)

Figure 7. Synthesis of (Z)-1-cyclohexyl-1-hexene employing 1-hexyne as starting material and applying alkenylborane and subsequent addition of iodine; reviewed by W. Carruthers [4] H11C6 H B

C6H11 H

C4H9

C

B-

H

C+ C

C H

1-hexyne

H

C4H9

H

H

C4H9 : ..I :

: I.. : I H

B

C C

C C H

B

C C+

+

I

C4H9

H

+ + Na + I + OH

C

C4H9

-

H

B C

I H C4H9

BH

I

C C

B

I

C4H9

=

H C4H9

B C C

=

H

I

H

: ..I +

: ..I +

I

H

B

C4H9 C C

H

H

I

I

C C

H

+ +B

+ I- =

C4H9

BI2C6H11

(75% Z)

Figure 8. Synthesis of (Z)-1-cyclohexyl-1-hexene employing 1-hexyne as starting material and applying alkenylborane and subsequent addition of iodine; mechanistic views

Similarly, 3-hexyne is transformed in (Z)-3-cyclohexyl-3-hexene [4]; Figure 9 shows the corresponding mechanism. The “anti” elimination of boron and the iodine atom, reassures the stereoselectivity of the observed alkenic product in the alkene-forming step [4]. H11C6 H B

C6H11 H

Et

C

C

Et

3-hexyne

C

+

B-

H

C C2H5

C2H5

B C

C2H5

C2H5

H

+ + Na + I + OH-

C

C C+

B C2H5

C2H5

+

: ..I :

: I.. : -

I

I H

H

B

C C

C C C2H5

C2H5 : ..I +

C2H5

I BC2H5

H C2H5

C C

I

I B C2H5

=

H C2H5

B C C

C2H5

I

=

: ..I +

Figure 9. Synthesis of (Z)-3-cyclohexyl-3-hexene employing 3-hexyne as starting material and applying alkenylborane and subsequent addition of iodine; mechanistic views. Downloadable from: Revista Boliviana

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Accepted 04 15 2015 Bravo et Vila

: ..

: ..

Vol. 32, No.1, pp. 15-23, Ene./Abr. 2015 31(2) 15-23, Jan./Apr. 2015 Published 04 30 2015 .

I

H

B

C2H5

H

C2H5

C C I

I

C C

C2H5

+ I =

+ +B

BI2C6H11

C2H5 (85% Z) (Z)-3-cyclohexyl-3-hexene

Figure 9. Synthesis of (Z)-3-cyclohexyl-3-hexene employing 3-hexyne as starting material and applying alkenylborane and subsequent addition of iodine; mechanistic view (Cont.)

Dialkylvinylboranes can be synthesized from dialkylhaloboranes and an internal alkyne in the presence of lithium aluminium hydride. These can react with iodine in the presence of methoxide to produce trisubstituted alkenes, stereoselectively. The two substituents of the alkyne are trans to each other [4]. (Z)-3-methyl-3-pentene was obtained from 2-butyne as Figure 10 shows [4]. The mechanism includes the iodine complex already exposed in Figures 7 to 9; see Figure 11. CH3

C

(C2H5 )2BBr

C CH3

(C2H5)2B

H C

1/4 LiAlH4, THF

2-butyne

CH3

CH3

I2, NaOH

C

CH3OH, -78º C

CH3

H C

C

C2H5

CH3 (74%)

Figure 10. Synthesis of (Z)-3-methyl-2-pentene, a tri-substituted alkene with the two original substituents in alkyne located in trans to each other; reviewed by W. Carruthers [4] Li+ H3Al-

H5C2 Br B

H

C2H5 Li+

AlH3 Li+ C

C

C2H5

H

:C- C CH3

BCH3

C2H5 B

CH3

C+ C

C2H5

+ AlH3 + LiBr

+ + Na OH

H CH3

CH3

B

CH3 C2H5

C C

H CH3

H CH3 : ..I :

+I .. :

I

Et

B-

CH3 C2H5

: ..I :

C2H5 C2H5 C C B I CH3

H CH3

CH3

I

Et I

B- C H 2 5 C C

I

+I .. :

: ..I :

+

: I.. :

C2H5

B C C

CH3

CH3

CH3

CH3

C2H5 H

H C C

I-

C2H5

B

C2H5

H C C

C2H5 CH3

2-butyne

C2H5

Br

C C+

H CH3

CH3

H C

C

+

CH3

C2H5

I2BEt

(Z)-3-methyl-2-pentene

Figure 11. Synthesis of (Z)-3-methyl-2-pentene, a tri-substituted alkene with the two original substituents in alkyne located in trans to each other; mechanistic views

Trisubstituted alkenes are also obtained from terminal alkynes by way of the corresponding 1-alkenyl iodides. Iodide is treated by butyl-lithium, trialkylborane and iodine. The trisubstituted alkene possesses the iodine of the alkenyl iodide replaced by an alkyl group coming from the borane with retention of configuration. ‘The stereochemistry of the product requires syn elimination of R2BI’ [4,7,8]. Figures 12 and 13 explain this synthesis. C6H13

C

C H

2-butyne

C2H5MgBr

C6H13

CuBr.(CH3)2S

H C C

C 2 H5

I2

C6H13

Cu(CH3)2S.MgBr2 C2H5

C C

H (1) C H Li 4 9

o

(2) (C2H5)B, -78 C

I

Figure 12. Trisubstituted alkene synthesis by iodination and subsequent treatment with butyl-lithium, trialkylborane and iodine; reviewed by W. Carruthers [4]

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Vol. 32, No.1, pp. 15-23, Ene./Abr. 2015 31(2) 15-23, Jan./Apr. 2015 Published 04 30 2015

Accepted 04 15 2015 Bravo et Vila

C6H13

H

H C C

Li+

B-(C2H5)3

C2H5

C6H13

I2

C C

.

C2H5

C2H5

(75%; 95% stereochemically pure)

Figure 12. Trisubstituted alkene synthesis by iodination and subsequent treatment with butyl-lithium, trialkylborane and iodine; reviewed by W. Carruthers [4] (Cont.) Et-Mg+Br

C6H13

C

H

C6H13

C H

Me

Et 2-butyne

C

.. ..S

+ Me

C

Et

S Me + Cu+ + Br..

IH

C6H13

Me + Mg+2 +2 Br-

Cu

MgBr2 Me

C6H13

H

I

C

I

CuMe2S.MgBr2 I+

.. ..

S Me

H

C6H13

(C2H5)3B

C C-: Li

C4H9-Li+

+

CuMe2S.MgBr2

I2

+

Et

I

+ I

Et

C

Et

CuMe2S.MgBr2

C C

MgBr2

H

C6H13

C C

H

C6H13

=

C C Et

Cu

C2H5

Me S+ Me + Br = CuBr.Me2S ..

+2 + Mg + Br

H

C6H13

Cu

..

;

C C:-

C4H9I

Li+ H

C6H13 C C Et

C6H13

+

-

H

Li BEt3

C

+

Li BEt3

C

C C

-

Et

C2H5

C6H13

Et

C2H5

C6H13

H Et

I- Li+

I- Li+

H

C6H13 Et

B-Et2

H BEt2

I

C

I

Et

Et

C C H BEt2

C6H13 C C

BEt

I+ .. :

C C I

-

Et

: ..I :

I+ : .. :

C2H5

H Et

C6H13

+

C

+

BIEt2 + LiI

Et

I

Figure 13. Trisubstituted alkene synthesis by iodination and subsequent treatment with butyl-lithium, trialkylborane and iodine; mechanistic views

The synthesis of trisubstituted alkenes can be achieved using allylic alcohols as starting material. This depends in its critical phase on the stereoselective epoxidation of allylic alcohols. Hence, (Z)-6-methyl-5-undecene was obtained by oxidation of the allylic alcohol 1 with t-butyl hydroperoxide and vanadium catalyst to selectively give rise to erythro-epoxide 2 that at its turn was converted to the vicinal diol 3 thanks to interaction with lithium dibutylcuprate. Stereospecific deoxygenation of the diol could be possible by interaction with N,N-dimethylformamide dimethyl acetal. The dioxolane derivative obtained is then decomposed by heating and by adding acetic anhydride to give rise to the Z-alkene [4]. The vanadium-t-butyl hydroperoxide react with the C=C of allylic alcohols making possible selective epoxidations. Reaction of 1 with t-C4H9OOH in the presence of vanadium acetylacetonate as catalyst gave 2 almost exclusively [4,9,10]. See Figures 14 and 15. C4H9

t-C4H9OOH VO(acac)2

HO

CH3 1

C4H9

O

H HO

Li(C4H9)2Cu o

CH3

ether, -26 C

CH C4H9 5 11 OH(CH3)2NCH(OCH3)2, 25oC

C5H11

C4H9

H HO

2

H H3C

CH3 3

O H

O

(CH3CO)2O

21

C5H11

o

130 C

N(CH3)2

Figure 14. Trisubstituted alkene synthesis from allylic alcohol; reviewed by W. Carruthers [4] Downloadable from: Revista Boliviana

C4H9

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H

CH3

REVISTA BOLIVIANA DE QUÍMICA Bolivian Journal of Chemistry Received 03 23 2015

O acac : CH3

Vol. 32, No.1, pp. 15-23, Ene./Abr. 2015 31(2) 15-23, Jan./Apr. 2015 Published 04 30 2015

Accepted 04 15 2015 Bravo et Vila

O

O CH2-

C CH2 C

CH2

O

C CH2 C O

CH3

.

-

VO(acac)2 : CH3

CH2

CH2

C CH2 C O

O

CH2 C

V O C

CH3

O

H

H

H

=

CH3

HO

CH3 _

..

_

..

(acac)2OV

t-bu

+O H H

CH3

.. .. O ..

.. ..

..

H

H

.. ..

=

CH3

H

CH3

HO

H

HO

H

H

.. ..

H

H.. _ O Li+

H

..

H HO

HO

CH3

H

C4H9

C4H9 =

H HO

CH3

H

C4H9-

CH3

C4H9 =

O

H HO

CH3

Li+ , Cu+ (C4H9)2-

CH3

C4H9

..

O

erythro H

HO

H H

HO

O

O

(acac)2OV

H

C4H9

t-bu

HO

+ O

=

CH3 H

t-bu

(acac)2OV

H

HO

H

_

.. .. O..

H

_ H

HO

H

t-bu

.. O +O H

H

H

HO

H

(acac)2OV

t-bu

O

=

H

VOacac2 H

+ O

..

O

H

(acac)2OV

t-bu

.. O O..

..

(acac)2OV

t-bu

O

C5H11 O- +CH3 Li

C5H11 Li+OO- + Li = HO CH3

C4H9 = H HO

C5H11 = H CH3

H

C5H11 CH3

..

OH

..

C5H11 CH3

NMe2 CH3O

C5H11 CH3

.. ..

..

H O

O + MeOH

+

O H + MeOH

HO

-H

O H Me

H+O

O+HCH3

C5H11 C4H9 H Me O

H +

=

C5H11 OH

.. C4H9

H HO

CH3

O + MeOH

C4H9

+

(CH3CO)2O H

N

Me2N H

O-

O NMe2

C5H11 CH3

O+CH3 OCH3

CH3 CH3

C4H 9 H

O

Me2N

H

Me2N H

H

H

C5H11 C4H9 +

C5H11 CH3

C4H9 H

H

H O+CH3 C4H9 H

N

CH3

3

C4H9

NMe2 H

CH3O

3

H HO

+ LiOH +

H CH

..

C4H9

+

OH

..

H CH

CH3

H HO

H 2O

OH

OH

OCH3 OCH3 H+

CH3

OH

.. ..

H

OLi

..

OLi

C4H 9 C5H11

..

C5H11

C4H9 C5H11

.. ..

C4H9

NMe2

H

C5H11 Me

+

HO O

NMe2

Figure 15. Trisubstituted alkene synthesis from allylic alcohol; mechanistic views

ACKNOWLEDGEMENTS The authors express their gratitude to Prof. Eduardo Palenque from the Department of Physics, Universidad Mayor de San Andrés, for his bibliographic support. REFERENCES 1.

Bravo, J. 2005, Bol. J. of Chem., 23, 1-10. (http://www.bolivianchemistryjournal.org, 2005).

Downloadable from: Revista Boliviana

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de Química. Volumen 32 Nº1. Año 2015

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REVISTA BOLIVIANA DE QUÍMICA Bolivian Journal of Chemistry Received 03 23 2015

Accepted 04 15 2015 Bravo et Vila

Vol. 32, No.1, pp. 15-23, Ene./Abr. 2015 31(2) 15-23, Jan./Apr. 2015 Published 04 30 2015

Bravo, J.A., Mollinedo, P., Peñarrieta, J.M., Vila, J.L. 2013, Bol. J. of Chem., 30, 24-41 (http://www.bolivianchemistryjournal.org, 2013) 3. Bravo, J.A., Vila, J.L. 2014, Bol. J. of Chem., 31, 61-67 (http://www.bolivianchemistryjournal.org, 2014) 4. Carruthers, W. Some Modern Methods of Organic Synthesis, Cambridge University Press, 3rd ed., 1987, Worcester, U.K., pp. 148-156, 374. 5. Zweifel, G., Steele, R.B. 1967, J. Am. Chem. Soc., 89, 2754. 6. Zweifel, G., Steele, R.B. 1967, J. Am. Chem. Soc., 89, 5085. 7. Lahima, N.J., Levy, A.B. 1978, J. Org. Chem., 43, 1279. 8. Levy, A.B., Angelastro R., Marinelli E.R. 1980, Synthesis, 845. 9. Sharpless, K.B., Michaelson, R.C. 1973, J. Am. Chem. Soc., 95, 6136. 10. Rossiter, B.E., Verhoeven, T.R., Sharpless, K.B. 1979, Tetrahedron Lett., 4733. 2.

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