Graduate Seminar presentation at iit Guwahati by anshuman Barali and Laddi Singh

Presentation for graduate seminar

1. Course Title:-CH 500 ( GraduateSeminar)
Axial-selectivity in Prins Cyclization Reaction: Synthesis of 4-
Iodotetrahydropyrans
,Chem. Lett. 2011, 40, 11761178
Presented By :-
Laddi Singh
Anshuman Bharali
M.Sc. 2
nd
year
Department Of Chemistry
Indian Institute of Technology, Guwahati
Guwahati-781039

2. Axial-selectivity in Prins Cyclization Reaction: Synthesis of
4-Iodotetrahydropyrans
Importance and applications of 4-halotetrahydropyrans :-
Structural features of many biologically active natural products
Act as a intermediate in organic synthesis

3. LITERATURE METHODS FORTHIS
WORK
Generally equatorial 4-halotetrahydropyrans are prepared using lewisacids
such as SnCl
4
, SnBr
4
, TiCl
4
etc.
There are limited methods for the synthesis of axial 4-Halo substituted
tetrahydropyrans. For example:-
Jasti, R.; Vitale, J.; Rychnovsky, S. D. J. Am. Chem. Soc. 2004,126,9904-9905.

4. Trӓff, A. M.; Janjetovic, M.; Ta, L.; Hilmersson, G. Angew. Chem. Int. Ed. 2013, 52,12073-12076.
Borkar, P; Weghe, P. V. D.; Reddy, B. V. S.; Yadav, J. S.; Gree, R. Chem. Commun. 2012,48,9316-9318.

5. WHATISPRINS CYCLIZATION ?

6. WHATISPRINS CYCLIZATION ?

7. WHATISPRINS CYCLIZATION ?

8. WHATISPRINS CYCLIZATION ?

9. WHATISPRINS CYCLIZATION ?

10. Synthesis of 4-iodotetrahydropyran
PRESENT WORK
Anil K. Saikia,* SomasekharBondalapati, Kiran Indukuri, and Paramartha Gogoi
Published on the web October 1,Chem. Lett. 2011, 40, 11761178 doi:10.1246/cl.2011.1176

11. Yield(%)Ratio of 1b:2b Iodide ion sourceLewis Acids (equiv.)Entr
y
461:1NaIBF
3
.Et
2
O(1)1
781:2.5TBAIBF
3
.Et
2
O(1)2
823:2_TMSI (1)/ 2,6-Lutidine3
911:1NaITMSCl(1)4
621:2TBAITMSCl(1)5
_NRTBAIInCl
3
(1)6
_NRTBAISc(OTf)
3
(1)7
_NRTBAIIn(OTf)
3
(1)8
130:1TBAITMSOTf(0.1)9
760:1TBAITMSOTf(1)10
501:1I
2
TMSOTf(1)11
1b 2b

12. GENERALIZED REACTION

13. GENERALIZED REACTION

14. EFFECT OF ELECTRON DONATING
SUBSTITUENTS
A B
When R = H 1 1
When R = OMe 1 2
Oxocarbenium ion

15. REACTIONWITHTBAB

16. CHARACTERIZATIONOF PRODUCT
X-ray Crystallographic Analysis
1
H –NMR analysis

17. In conclusion, they have developed an axial-selective Prins-cyclization reaction with high
diastereoselectivityand good yields.
The 4-axial halosubstitutedproducts would be an important synthetic intermediate for
the synthesis of 4-equatorial substituted tetrahydropyrans by substitutionreactions.
CONCLUSIONS
References:-
1. Trӓff, A. M.; Janjetovic, M.; Ta, L.; Hilmersson, G. Angew. Chem. Int. Ed. 2013, 52,12073-12076.
2. Borkar, P; Weghe, P. V. D.; Reddy, B. V. S.; Yadav, J. S.; Gree, R. Chem. Commun. 2012,48,9316-9318.
3. Jasti, R.; Vitale, J.; Rychnovsky, S. D. J. Am. Chem. Soc. 2004,126,9904-9905.