![INTRODUCTION
The [3 + 2] 1,3-dipolar cycloaddition is a reaction where two organic
compounds, a dipolarophile, and a 1,3-dipole (or ylide), combine to
form a five membered heterocycle
B
A
C
R2
R1 R1
A
B
C
R2
+
R3
R4
C
B
AR2 R1
R4R3
This reaction is often used as a key step in many natural products and
pharmaceuticals synthesis
The asymmetric variants of this reaction using either chiral auxiliaries or chiral
catalysts are relatively new research fields and have attracted a continually
growing interest](https://image.slidesharecdn.com/13-dipolarcycloadditions-160909194941/85/1-3-dipolar-cycloadditions-2-320.jpg)
1,3 dipolar cycloadditions
- 1. RECENT ADVANCES IN 1,3-DIPOLAR CYCLOADDITIONS JAYANTA SAHA IIT ROPAR 2015CHS1003
- 2. INTRODUCTION The [3 + 2] 1,3-dipolar cycloaddition is a reaction where two organic compounds, a dipolarophile, and a 1,3-dipole (or ylide), combine to form a five membered heterocycle B A C R2 R1 R1 A B C R2 + R3 R4 C B AR2 R1 R4R3 This reaction is often used as a key step in many natural products and pharmaceuticals synthesis The asymmetric variants of this reaction using either chiral auxiliaries or chiral catalysts are relatively new research fields and have attracted a continually growing interest
- 3. The Dipolarophile The dipolarophile in a 1,3-dipolar cycloaddition is a reactive alkene moiety containing 2 electrons. Thus, depending on which dipole that is present, 留,硫unsaturated aldehydes, ketones, and esters, allylic alcohols, allylic halides, vinylic ethers and alkynes are examples of dipolarophiles that react readily
- 4. The 1,3-dipole/ylide The 1,3-dipole, also known as an ylide, bears a positive and a negative charge distributed over three atoms and has 4 electrons. The most common atoms incorporated in the 1,3-dipole are nitrogen, carbon, oxygen or sulfur. These are divided into two groups, the allyl anion type which has a bent structure and the propargyl/allenyl anion type with a linear structure
- 6. Mechamisms for the 1,3-DC reaction The 1,3-dipolar cycloaddition reaction of a 1,3-dipole with a dipolarophile involves the 4 electrons of the dipole/ylide and the 2 electrons of the dipolarophile. The reaction mostly proceeds in a concerted manner, which means that all bonds are created simultaneously Depending on the nature of the dipole and the dipolarophile, the 1,3-dipolar cycloaddition reaction is controlled either by a LUMO(dipolarophile)- HOMO(dipole)- or a LUMO(dipole)-HOMO(dipolarophile) interaction but insome cases both interactions is involved .
- 7. Mechamisms for the 1,3-DC reaction
- 8. The classification of the 1,3-DC reactions onthe basis of the FMOs NITRONE NITRILE OXIDE Azomethine imine Diazoalkene Nitosooxide Ozone
- 9. The change in frontier orbitals by coordination of a Lewis acid Type II
- 10. Recent Literature 1,3-Dipolar cycloaddition reactions of azomethine ylides with aromatic dipolarophiles General reaction Examples of isoindole-containing natural products, pharmaceuticals and dyes: (+)-staurosporine 4 (indolocarbazole alkaloid), mitiglinide 5 (type 2 diabetes),46 lenalidomide 6 (anticancer, multiple myeloma), and Pigment Yellow 139 7 (dye).
- 11. 1,3-Dipolar cycloaddition reactions of azomethine ylides with aromatic dipolarophiles Some products formed in this manner Main reaction John H. Ryan,ARKIVOC 2015 (i) 160-183
- 12. Methods for asymmetric 1,3-DC reactions of Nitrones with Alkenes Pellissier, H. Tetrahedron 2007, 63, 3235-3285
- 13. N H Ph X H H exo endo Stereoselectivity Regioselectivity EDG H NPh H NPh EWG head-to-head head-to-tail N H Ph H H XN H Ph N H Ph X X N H Ph EDG N H Ph EWG General Approach to the Selectivity in 1,3-Dipolar Cycloadditions
- 14. Acylaziridines Methods for asymmetric 1,3-DC reactions of Nitrones with Alkenes
- 15. J.Org. Chem. 1995, 60, 4999 + Methods for asymmetric 1,3-DC reactions of Nitrones with Alkenes
- 16. Application of cycloaddition reaction in natural product synthesis