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Ch24 - Chapter 24 Carbon-Carbon Bond Formation a'nd...

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Chapter 24: Carbon-Carbon Bond Formation a'nd Synthesis Solutions 662 CHAPTER 24 Solutions to the Problems PrQblem 24. L ShQW hQW YQU might prepare each cQmpQundby a Heck reactiQn using methyl 2-prQpenQate as the starting alkene. OCH:3 (a) (the £ iSQmer) ~I + 1# & (b) (the 2£,42 iSQmer) Chapter 24: Carbon;Carbon Bond Formation and Synthesis Solutions 663 PrQblem 24.3 ShQW hQW the fQIlQwing cQmpQulJd can be prepared from starting materials containing eight carbons Qr less. 8r ---( )-OMe or Orv1e NaOH Because both pieces are aryl, there are two combinations of reagents that would work for a Suzuki coupling to make the biaryl product. Note that a borane or boric ester could also have been used. Problem 24 4 ShQW the product Qf the fQllowing reactiQh. 5 0 4 nucleophilic carbene catalyst . ~ 2 Numbers were added to help you keep track of the different atoms as the ring is formed. The alkene metathesis reaction will generate an eleven-membered ring by forming a bond between carbon atoms labeled as 2 and 12. Carbons labeled as 1 and 13 will be found in the ethene product. Problem 24.5 What cQmbination Qf diene and dienQphile undergQes Diels-Alder reactiQn tQ give each adduct. (a) ( + ~ cr CXX:CH:3 CH300CyCOOCH3 + Utocx;H 3 ( (b) COOCH 3 C CX=H3 .. + III I ( I (c) C I COOCH 3 COOCH 3 In each part of this problem, the diene is 1,3-butadiene. In (a); the dienophile is one of the double bonds of a second molecule of 1,3-butadiene. In part (b), the dienophile is a 1,1·disubstituted alkene and in part (c), it is a disubstituted alkyne. . .~ H 2 C=CH-COCH 3 Methyl 2-propenoate (Methyl acrylate) OCH:3 cat. Pd( OAc) 2 .. o cat. Pd( OAch PPh 3 , ~ CO:!, +~I DMF Problem 24.2 Give reagents and conditiQns fQr the fQlIQwing reactiQn. Ph Ph 8rylrsr + 6 Pd(OAch, 2 Ph 3 P .. B- Ph B-Ysr Styrene Ph· Reaction of hexabromobenzene with 6 equivalents of styrene under the normal Heck conditions gives the desired compound.
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664 Solutions Chapter 24: Carbon-Carbon 130nd Fonnation and Synthesis Problem 24.6 Which molecules can function as dienes in Diels-Alder reactions? Explain your reasoning. (a) (b) (c) o o -0 To function as a diene, the double bonds must be conjugated and able to assume an s-cis conformation. Both (a) 1,3-cyclohexadiene and (c) 1,3.cyclopentadiefie can function as dienes. The double bonds in (b) 1,4 - cyclohexadiene are not conjugated and, therefore, this molecule cannot function as a diene. Problem 24.7 What diene and dienophile might you use to prepare the following racemic Diels-Alder adduct? ri~COOCH3 ~~H COOCH 3 Use cyclopentadiene and the E-alkene.· Note that two new chiral centers are formed in the reaction so the product is actually a racemic mixture of the two enantiomers having a trans arrangement of the ester groups. HXCOOCH3 _ri~COOCH3 o .-+ I ---. ~HH + CH 3 00C H COOCH 3 Problem 24.8 Show how to synthesize allyl phenyl ether and 2-butenyl phenyl ether from phenol and appropriate alkenyl halides.
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