Solns1-27-06

Solns1-27-06 - CHEM 252; HONORS ORGANIC CHEMISTRY ll Spring...

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Unformatted text preview: CHEM 252; HONORS ORGANIC CHEMISTRY ll Spring 2005 Dr. David J. Lapinsky 1 / 27 / 06 Problem Session: Dienes and the Allyl System: 2p Orbitals in Conjugation 1.) Provide a mechanism for the formation of compound B from compound A and explain why alkyne C is not produced. NaNH2 / NH3 then H20 w NOT /\/\/\ M \ C A B 2.) Allyl ethers (D) can be thought of as a masked combination of an aldehyde (F) and an alcohol (E). Write a detailed electron pushing mechanism for the following reaction. n-BuLi then 0 H O+/H O D E F (an allyl ether) (an alcohol) (an aldehyde) 3.) Outline the two Williamson ether synthesis strategies you could use to make compound 9D. Which reaction would you predict is faster? Explain your answer by drawing and explaining the transition states for the reactions. 4.) Using an appropriate alkyne and 1-bromopropane as your starting materials, suggest reasonable syntheses for the following molecules. 4a.) M 4b.) 4c.) \/\n/\/\ O 5.) Synthetic estrogen analogs are tremendously important molecules with respect to human health. They can serve as replacement therapy for post- menopausal women helping to prevent osteoporosis, are found in oral contraceptives (i.e. birth control pills), and serve as lead molecules in the development of agents to treat breast cancer. As a result, synthetic methodology for the development of estrogen analogs is an important field of medicinal chemistry affecting the lives of millions. Estradiol (E) is the principal human estrogen and it can be made via Diels-Alder methodology. Give the structure of the Diels-Alder precursor (F) that is ultimately derived from compound G and propose mechanisms for the transformations of G to F and Fto E. HO heat Diels—Alder heat Diels-Alder pref?” 0” Estradioll (E) Fl G (Hints: Draw another resonance form for the phenyl ring of estradiol, then ask yourself what kind of rings due Dials-Alder reactions make.) 6.) Propose a mechanism for the following transformation. o 0 heat H SO \ O O 7.) Propose a mechanism for the following reaction. /\/\/\ | \ / \ __._—..__—> 0 heat / O 8.) The following reaction comes from the synthesis of pseudoabersonine. Provide a mechanism for this transformation. 9.) Via analyzing the resonance forms of the starting materials, explain the regioselectlvity of the following Diels-Alder reaction. ' 0 f + -———> + M60 \ O U 92% 8% HNIH AH W b \ /\/ ® Q$$tn,\74\\\{ QazvchJ-Ae. s’rtes and dual (kn *0 ;;r\a\ Ptodgcfi GDI'MG‘M an "4‘: (mth ‘ \ - , ‘r\u(.!\\IQ 'FOfMuh an _ ‘ o\\< h ~ IS (\o“ Yo;:1h\e 5 an are) WV“ ck 63‘) <5 W . Q\ NO m + L w ES’ /\/O\/\ @ LC” 6” ow: © T5 FO( Q\ T5 FM ¥ , C313. i g l ’ }3 CH5 ; f : i; \ i C' 2 Q] Q e W CH3 a3? Sea 56 \ a 4K A. 9‘0“ L 1 ’3 af 0’ H i H I 2, UV; H H $*A¥\\1A* an 13$ HO $«J\?or*:r\¢3 S’fob‘MZ‘g‘ a“ TS 0? TS \ow¢.( finz‘S" N \u kqahtf We‘aYTS \oth E‘\ \H \\\ (K Eq FOS*%( n \\\ r F'xn LDA [NH NQNH 5 \ .H‘e'fi // M—‘fi—fi ‘\\'\E.¢'\ / Nffir H30 (mm H». Lgrd‘m“ Lug) _ :. i—a OA\ ’— erm L‘“‘\\“ 7 /\/e’( [v Nas 1% 6r +O\< h M ‘\ (EEG /’ as LDA / “‘1‘;th /\ / \-—— -— H 0 New H3O OH DA "\ gonfiéued affix! (“9.0 (“go (9 )‘oo‘\ \iou‘kquth ED ( QFQQC‘ {Tom “at SIOWL“ grog? ‘ 1“ H is on “mice, (or A (mazon' E) m: or ‘Hxa‘k + he. Pk emu, b ‘k Matte. reatanonzz 'Canfig are. seaglyk-As u V4 «q 42 cm EDC: ring is ad”. ‘\"r\ ‘“‘\e Phanxfl ‘3‘- (QKOnaan S‘Tu(‘.v\u(¢_3 Sue€o‘ ‘ 3 E) /‘_. 533 DA mo -* * '> \ fl/él Ara“; casuananoi FHMS ‘ 86> O {o( o'Umu dams 6 ,7 <ma$0"\ («INA _ _ ENC? anx AJQAOPKLVLS *0 QKPA‘” \IS. _E.OC-; (Q63ch chamls’h'x/ (52°. 9% ‘36 (~ffi‘.no(\ (8‘!o\ - kaCk do \‘c-u Jm'mk £5 Mme my” Wang? ...
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This note was uploaded on 05/03/2008 for the course CHEM 252 taught by Professor Billups during the Spring '08 term at Rice.

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Solns1-27-06 - CHEM 252; HONORS ORGANIC CHEMISTRY ll Spring...

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