Question

Please help me find the overall yield of transformation of 4 to 7 using this info!!

afforded the seco -263。 was obt The a biguous corresp (3闷-fluorothlidomide(MJ) (3S)-fluoro thalidomide ((SJ) Figure 1. The use of fluorine substitution in our approach has many precedents. Because the flourine atom is the smallest atom other than hydrogen, flourine is the best possible atom to substite for hydrogen in designing isosteric analogues." High electronegativity and a strong C-F bond are added factors that have made the introduction of fluorine into biologically active compounds a very effective approach for developing new drugs.12 In our example, the resistance of the enanti- omers of 3-fluorothalidomide (3) to racemization and the close structural similarity to thalidomide itself render 3 an excellent candidate in the search for safe thalidomide-based drugs in which the sedative effects of 1 can be clearly separated from teratogenicity. Attempted direct fluorination of thalidomide (1) or N- phthalylglutamic anhydeide under various conditions did not give the corresponding fluorinated product. However, the preparation of 3 was finally carried out efficiently as follows: N-tert-butoxycarobonyl-3-phthalimidopiperidin-2- one (5), prepared from the readily available 3-phthalimidyl- piperidin-2-one (4)13 by treatment with Boc20 in acetonitrile, from was deprotonated with 1.2 equiv of LiHMDS in THF at -40 butyl °C (Scheme 1). Introduction of an excess of diluted per- and chloryl fluoride 14 gave fluorinated compound 6 in 71% yield. 2-na The Boc room temperature to furnish 7. Finally, oxidation'5 of 7 was stab 1572 group of 6 was then removed by TFA treatment at In

Answer 1

From the information given,

yield from (4) to (6) is 71% and then from (6) to (7) is 90%.

Now, assuming that the reagents used are in excess in every step, say we started with 1 mole of (4) and reach (6) with 71% yield. Thus, we obtained 0.71 moles of (6) from 1 mole of (4). Now, this 0.71 moles of (6) was used to produce (7) with 90% yield. Hence, moles of (7) produced= 0.71*0.9 = 0.639

i.e., the yield for transformation from (4) to (7) is 63.9%.