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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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
.
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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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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=
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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
de Química. Volumen 32 Nº1. Año 2015
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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
22
de Química. Volumen 32 Nº1. Año 2015
http://www.bolivianchemistryjournal.org, http://www.scribd.com/bolivianjournalofchemistry
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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.