WE CLAIM
1. An improved process for the preparation of Selinexor, comprising the steps of:
a) N-alkylation of triazole compound of formula (II) to obtain the N-alkylated ester of formula (IV), wherein X may be hydrogen, Y may be a leaving group such as a halogen or a sulphonate group (or) X and Y may together form a triple bond between carbons atoms to which there are linked and R may be an optionally substituted alkyl, optionally substituted aryl, optionally substituted arylalkyl, optionally substituted heteroaryl group;

optionally purifying the N-alkylated ester of formula (IV);
c) hydrolysis of the N-alkylated ester of formula (IV) of step a) or step b) to corresponding N-alkylated acid of formula (IVa);

d) purifying the N-alkylated acid of formula (IVa) through formation of its addition salt of formula (VI), wherein B is a base;

Selinexor of formula (I), wherein Z may be hydrogen or a protecting group.
f) optionally, removing the protecting group to obtain Selinexor. 2. A process for the preparation of Selinexor or a salt thereof, comprising the steps of:
a) N-alkylation of triazole compound of formula (II) to obtain the N-alkylated ester of formula (IV), wherein X may be hydrogen and Y may be a leaving group such as a halogen or a sulphonate group (or) X and Y together form a triple bond between carbons atoms to which there are linked, R may be an optionally substituted alkyl, optionally substituted aryl, optionally substituted arylalkyl, optionally substituted heteroaryl group;

d) Optionally, removing the protecting group to obtain Selinexor.
e) purifying the Selinexor obtained in step c) or d).
3. An addition salt of N-alkylated acid of formula VI with an inorganic or organic base selected from the group comprising of mono-, di- and trisubstituted amines such as, Dicyclohexylamine(DCHA), tert-Butyl amine, diethyl amine, dibutylamine, Morpholine, 3-diemthylamino-1 -propylamine, diisopropyl amine, N-tert-butylbenzylamine, N-benzylmethylamine, a-Methyl benzyl amine, (s)-a-methyl benzylamine, benzyl amine,

dibenzylamine, cyclohexyl amine, tert-octylamine. Tris(hydroxymethyl)aminomethane, 2-Amino-2-methyl-l - propanol, 2-Amino-2-methyl-1,3-propanediol, 2,2'-(Propane-l,3-diyldiimino)bis[2-(hydroxymethyl)propane-l,3-diol],2-[Bis(2-hydroxyethyl)imino]-2-(hydroxymethyl)-1,3-propanediol, 2-Aminoethanol, (2R,3R,4R,5S)-6-Methylaminohexane-1, 2,3,4, 5-pentol, 2,2',2"-Nitrilotriethanol.
4. A process for the preparation of Selinexor comprising the step of preparing an addition salt of N-alkylated acid of formula VI.
5. A crystalline Form-Delta of Selinexor, characterized by a PXRD pattern comprising the peaks at 6.11, 12.16, 13.00, 20.28 and 24.43 ±0.2° 20.
6. A crystalline Form-Delta of Selinexor of claim 5, further characterized by one or more additional peaks at 19.35, 23.39 and 23.78 ±0.2° 20.
7. A crystalline Form-Epsilon of Selinexor, characterized by a PXRD pattern comprising the peaks at 5.87, 11.72, 17.61, 18.68, 20.50, 22.78, 23.20, 23.53 and 23.97 ±0.2° 20.
8. A crystalline Form-Epsilon of Selinexor of claim 7, further characterized by one or more additional peaks at about 16.26, 21.25, 25.35, 29.22 and 30.14±0.2° 20.
9. A crystalline Form- Zeta of Selinexor, characterized by a PXRD pattern comprising the peaks at 4.86, 6.99, 7.74, 10.86, 15.50 and 19.47 ±0.2° 20.

10. A crystalline Form- Zeta of Selinexor of claim 10, further characterized by one or more additional peaks at 14.00, 18.27,20.73,21.51 and 22.14 ±0.2° 20.
11. A crystalline Form-Eta of Selinexor, characterized by a PXRD pattern comprising the peaks at 3.54, 7.03, 9.91, 11.59, 19.84, 20.44 and 21.64 ±0.2° 20.
12. A crystalline Form-Eta of Selinexor of claim 11, further characterized by one or more additional peaks at 17.55, 21.09, 22.45 and 23.28 ±0.2° 20.
13. A crystalline Form-Theta of Selinexor, characterized by a PXRD pattern comprising the peaks at 6.96, 13.92, 20.95 and 22.82 ±0.2° 20.
14. A crystalline Form-Theta of Selinexor of claim 13, further characterized by one or more additional peaks at about 17.24, 20.03, 20.37 and 23.41 ±0.2° 20.
15. A crystalline Form- Iota of Selinexor, characterized by a PXRD pattern comprising the peaks at 3.69, 7.33, 11.01, 14.66, 16.19 and 18.36 ±0.2° 20.
16. A crystalline Form- Kappa of Selinexor, characterized by a PXRD pattern comprising the peaks at 3.22, 11.71, 12.56, 14.42 and 25.20 ±0.2° 20.
17. A crystalline Form-Lambda of Selinexor, characterized by a PXRD pattern comprising the peaks at 12.61, 19.00, 19.95 and 21.29 ±0.2° 20.
18. A crystalline Form-Lambda of Selinexor of claim 17, further characterized by one or

more additional peaks at 14.13, 21.29, 21.75, 23.10, 24.65 and 30.86 ±0.2° 20.
19. A crystalline Form-Mu of Selinexor, characterized by a PXRD pattern comprising the peaks at 9.31, 17.45, 17.85 and 22.72 ±0.2° 20.
20. A crystalline Form-Mu of Selinexor of claim 19, further characterized by one or more additional peaks at 21.20, 25.01 and 27.59 ±0.2° 20.
21. A crystalline Form- Nu of Selinexor, characterized by a PXRD pattern comprising the peaks at 10.75, 17.52, 21.84, 22.16 and 22.38 ±0.2° 20.
22. A crystalline Form-Nu of Selinexor of claim 21, further characterized by one or more additional peaks at about 18.30, 24.53 and 28.91 ±0.2° 20.
23. A crystalline Form-Xi of Selinexor, characterized by a PXRD pattern comprising the peaks at 10.54, 11.68, 12.72 and 24.56 ±0.2° 20.
24. A crystalline Form-Xi of Selinexor of claim 23, further characterized by one or more additional peaks at about 3.70, 7.36, 18.10, 19.72 and 21.21 ±0.2° 20.
25. An amorphous form of Selinexor.
26. A pharmaceutical composition comprising amorphous form of Selinexor combined with atleast one pharmaceutically acceptable excipient.
27. An amorphous solid dispersion of Selinexor together with atleast one pharmaceutically acceptable excipient.
28. A pharmaceutical composition comprising amorphous solid dispersion of Selinexor combined with atleast one additional pharmaceutically acceptable excipient.
29. A pharmaceutical composition comprising Selinexor and atleast one pharmaceutically acceptable excipient, wherein Selinexor may be selected from group comprising of crystalline Form-Delta, Form-Epsilon, Form-Zeta, Form-Eta, Form-Theta, Form-Iota, Form-Kappa, Form-Lambda, Form-Mu, Form-Nu and Form-Xi of Selinexor or mixtures thereof.
30. A process for preparing a crystalline Form-Alpha of Selinexor, which comprises:

a) combining Selinexor with acetone: water mixture;
b) stirring the mixture of step a);
c) isolating crystalline Form-Alpha of Selinexor.
31. A process for preparing a crystalline Form-Delta of Selinexor, which comprises:
a) combining Selinexor with methanol;
b) stirring the mixture of step a);
c) isolating crystalline Form-Delta of Selinexor.
32. A process for preparing a crystalline Form-Epsilon of Selinexor, which comprises:

a) combining Selinexor with ethanol;
b) stirring the mixture of step a);
c) isolating crystalline Form-Epsilon of Selinexor.
33. A process for preparing a crystalline Form-Zeta of Selinexor, which comprises:
a) combining Selinexor with acetic acid and water;
b) stirring the mixture of step a);
c) isolating crystalline Form-Zeta of Selinexor.
34. A process for preparing a crystalline Form-Eta of Selinexor, which comprises:
a) combining Selinexor with nitromethane;
b) stirring the mixture of step a);
c) isolating crystalline Form-Eta of Selinexor.
35. A process for preparing a crystalline Form-Theta of Selinexor, which comprises:
a) providing a solution of Selinexor in formic acid;
b) contacting the solution of step a) with an anti-solvent;
c) isolating crystalline Form-Theta of Selinexor.

36. A process for preparing a crystalline Form-Iota of Selinexor, which comprises the step of drying Form-Eta of Selinexor.
37. A process for preparing a crystalline Form-Kappa of Selinexor, which comprises:

a) combining Selinexor with water;
b) stirring the mixture of step a);
c) isolating crystalline Form-Kappa of Selinexor.
38. A process for preparing a crystalline Form-Kappa of Selinexor, which comprises:
a) providing a solution of Selinexor in methanol or a mixture thereof;
b) contacting the solution of step a) with water;
c) isolating crystalline Form-Kappa of Selinexor.
39. A process for preparing a crystalline Form-Lambda of Selinexor, which comprises:
a) combining Selinexor with glycerol;
b) stirring the mixture of step a);
c) isolating crystalline Form-Lambda of Selinexor.
40. A process for preparing a crystalline Form-Mu of Selinexor, which comprises:
a) combining Selinexor with dimethyl formamide;
b) stirring the mixture of step a);
c) isolating crystalline Form-Mu of Selinexor.
41. A process for preparing a crystalline Form-Nu of Selinexor, which comprises:

a) combining Selinexor with dimethylacetamide;
b) stirring the mixture of step a);
c) isolating crystalline Form-Nu of Selinexor.

42. A process for preparing a crystalline Form-Xi of Selinexor, which comprises the step of drying Form-kappa of Selinexor.
43. A process for the preparation of crystalline form of Selinexor or a solvate thereof, comprising the step of converting amorphous Selinexor to crystalline form of Selinexor or a solvate thereof.
44. A process for the preparation of an amorphous form of Selinexor, comprising the steps of:

a) providing a solution of Selinexor in a solvent or a mixture thereof;
b) removing the solvent from the solution obtained in step a); and
c) isolating the amorphous form of Selinexor.
d) optionally combining amorphous form of step c) with atleast one pharmaceutically acceptable excipient.
45. A process for the preparation of an amorphous solid dispersion of Selinexor,
comprising the steps of:
a) providing a solution of Selinexor and atleast one pharmaceutically acceptable excipient in a solvent or a mixture thereof;
b) removing the solvent from the solution obtained in step a), and
c) isolating the amorphous solid dispersion of Selinexor.
d) optionally combining amorphous solid dispersion of step c) with atleast one additional pharmaceutically acceptable excipient.