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Scheme I. Optimised Procedures for Obtaining Pure Enantiomers of 2 and 3 5 (286 mg) Recipicstc Solution workup and 4 chromarography (+2: 54 mg (19%) (+)-2: 140 mg (49%) [ a ]~ -134' (84% W ) ID +5OO (31% ee) 1 4 crysrdlization (-1-2: 37 mg (13% overall) (+>2: 62 mg (22% overall) [ a ]~ -1590 (-10046 et) [ a ]~ +158O (--10046 CC) 4 (144 mg) + 5 (143 mg) Recipifatc coupling A Solution workup and 4 chromatography (-)-3 122 mg (43%) (+)-3 121 mg (42%) [a], -540 (46% cc) [a], +540 (46% ee) Crystals: 26%; [ab -3O crystals: 21% [a], +40 Mother liq,: 74%; [ a ]~ -72O (61% ee) Mother liq.: 78%; [a], +73O (62% ee) 4 4 crydlizarion of mother liquors (-)-3 66 mg (23% overall) (+)-3: 68 mg (24% overall) [ a l~ -1170 (2 98% et) [ a ]~ +I 16' (-97% CC) at rt for 20 h under an argon atmosphere. Then concd HCl(5 mL) was added, followed by water (100 mL). The precipitate was filtered off, suspended in acetone with silica gel (20 g), and chromatographed on a silica gel column (40 g) using a light petmleum-ether mixture (1:l) as eluent. The eluate was evaporated to afford 1 (43 mg; 14%): mp 205-207 "C (no depression was observed for a mixture with an authentic sample of enantiome r i d y pure 1); [a]D -No (c 5.0, THF; 100% ee) 0it.U mp 207-209 "C and ["ID -35.5" or -33.4O, respectively, for optically pure compound and [ a ] D +34.3" for the enantiomer.) Analogous workup of the solution furnished 1 (121 mg; 42%): mp 210-214 (B) By Deracemization of (&)-l. To a degassed solution of CuC12.4H20 (200 mg; 1 mmol) in methanol (10 mL) was added a solution of (-)-sparteine (468; 2 mmol) in methanol (10 mL), and the mixture was stirred at rt for 10 min under argon. A solution of (&)-I (286 mg; 1 mmol) in degassed methanol (10 mL) was added, and the mixture was stirred under argon at rt for 20 h. The mixture was then worked up as above to give 1 (267 mg; 94%): mp 212-214 OC; [ a ] D -27.2' (c 5.0, THF; 80% ee). For further resolution, see the text. (S)-(-)-

The beginning of 1970’s may well be regarded as turning point in the area of organic synthesis when an efficient and straight forward strategy for the reaction of primary and/or secondary alcohols with variety of nucleophiles in the presence of triphenylphosphine and azodicarboxylate reagent was discovered by O. Mitsunobu and since then rapid progress has been made in understanding and applying the Mitsunobu reaction for various derivatization reactions. Due to versatile applications and mild reaction conditions associated with the said strategy, the Mitsunobu reaction has received much attention in the last almost fifty years and has been well reported. The basic objective of this review is to pay attention on the recent advances and applications of the Mitsunobu reaction particularly in last decade. The attention has also been paid to describe various modifications which have been explored in the traditional Mitsunobu reaction by substituting P (III) reagents or azodicarboxylate reagents with other suitable reagents or else using an organocatalyst with the objective to improve upon the traditional Mitsunobu reaction. In the present review we wish to report the major advancements achieved in last few years which are likely to be beneficial for the researchers across the globe.

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