ALDEHYDES AND KETONES: NUCLEOPHILIC ADDITION TO THE CARBONYL GROUP 433 C6HSCCH3+ CH-CCH H2o CHC=CH2 Piperidine Carbinolamine Here we see an example of the Wittig reaction applied to diene synthesis by use of an ylide containing a carbon-carbon double bond CHaCHCH,CH +(C6H5)3P--CHCH=CH CH, CH, CH, CH=CHCH=CH, +(CKHsaP-0 Butanal Allylidenetriphenylphosphorane 1, 3-Heptadiene(52%) Triphenylphosphine (c) Methylene transfer from methylenetriphenylphosphorane is one of the most commonly used Wittig reactions CH3+(CH)一(H2 CCH3+(C6H5)3P一 Cyclohexyl methyl Methylenetriphenyl- 2-Cyclohexylpropene Triphenylphosphine phosphorane 17.14 A second resonance structure can be written for a phosphorus ylide with a double bond between phosphorus and carbon. As a third-row element, phosphorus can have more than 8 electrons in its (CHS)3P- →(C6H5)3P=CH2 Methylenetriphenylphosphorane 17.15 (b) Two Wittig reaction routes lead to 1-pentene. One is represented retrosynthetically by the disc CH, CH, CH, CH=CH, CH,CH, CH,CH +(C H5)3P--CH 1-Pentene Methylenetriphenyl The other route is CH_ CH, CH, CH=CH? CH, CH,CH2CH--P(C6H5)3+ Back Forward Main Menu TOC Study Guide Toc Student OLC MHHE Website(c) 17.13 (b) Here we see an example of the Wittig reaction applied to diene synthesis by use of an ylide containing a carbon–carbon double bond. (c) Methylene transfer from methylenetriphenylphosphorane is one of the most commonly used Wittig reactions. 17.14 A second resonance structure can be written for a phosphorus ylide with a double bond between phosphorus and carbon. As a third-row element, phosphorus can have more than 8 electrons in its valence shell. 17.15 (b) Two Wittig reaction routes lead to 1-pentene. One is represented retrosynthetically by the disconnection The other route is 1-Pentene CH3CH2CH2CH CH2 Formaldehyde O HCH Butylidenetriphenylphosphorane CH3CH2CH2CH P(C6H5)3 1-Pentene CH3CH2CH2CH CH2 CH3CH2CH2CH O Butanal Methylenetriphenyl￾phosphorane CH2 (C6H5)3P Methylenetriphenylphosphorane (C6H5) CH2 3P CH2 (C6H5)3P CCH3 O Cyclohexyl methyl ketone CCH3 CH2 2-Cyclohexylpropene (66%) Triphenylphosphine oxide O (C6H5)3P Methylenetriphenyl￾phosphorane (C6H5)3P CH2 Allylidenetriphenylphosphorane 1,3-Heptadiene (52%) Triphenylphosphine oxide Butanal CH3CH2CH2CH CH3CH2CH2CH O (C6H5)3P CH CHCH 2 CHCH CH2 (C6H5)3P O Carbinolamine intermediate 1-Piperidino-1- phenylethene Acetophenone Piperidine C6H5CCH3 O H C6H5CCH3 OH H2O C6H5C CH2 N N N ALDEHYDES AND KETONES: NUCLEOPHILIC ADDITION TO THE CARBONYL GROUP 433 Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website