1 / 20

14.11 Alkane Synthesis Using Organocopper Reagents

14.11 Alkane Synthesis Using Organocopper Reagents. Dr. Wolf's CHM 201 & 202. 14-53. Lithium Dialkylcuprates. Lithium dialkylcuprates are useful synthetic reagents. They are prepared from alkyllithiums and a copper(I) halide. 2RLi + Cu X. R 2 Cu Li + Li X.

alfreda-burt
Télécharger la présentation

14.11 Alkane Synthesis Using Organocopper Reagents

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 14.11Alkane Synthesis Using Organocopper Reagents Dr. Wolf's CHM 201 & 202 14-53

  2. Lithium Dialkylcuprates Lithium dialkylcuprates are useful synthetic reagents. They are prepared from alkyllithiums and a copper(I) halide. 2RLi + CuX R2CuLi + LiX [customary solvents are diethyl ether and tetrahydrofuran (THF)] Dr. Wolf's CHM 201 & 202 14-54

  3. R Li R Cu Cu I How? the alkyllithium first reacts with the copper(I) halide Li+ I– Dr. Wolf's CHM 201 & 202 14-55

  4. R Li R Cu Cu I R R Li R Cu R Cu How? the alkyllithium first reacts with the copper(I) halide Li+ I– then a second molecule of the alkyllithium reacts with the alkylcopper species formed in the first step Li+ – Dr. Wolf's CHM 201 & 202 14-56

  5. + + + R'X LiX R R' RCu R2CuLi Lithium diorganocuprates are used toform C—C bonds + + + R'X LiX Ar R' ArCu Ar2CuLi Dr. Wolf's CHM 201 & 202 14-57

  6. Example: Lithium dimethylcuprate + (CH3)2CuLi CH3(CH2)8CH2I primary alkyl halides work best (secondary and tertiary alkyl halides undergo elimination) diethyl ether CH3(CH2)8CH2CH3 (90%) Dr. Wolf's CHM 201 & 202 14-58

  7. Example: Lithium diphenylcuprate + (C6H5)2CuLi CH3(CH2)6CH2I diethyl ether CH3(CH2)6CH2C6H5 (99%) Dr. Wolf's CHM 201 & 202 14-59

  8. CH2CH2CH2CH3 Vinylic halides can be used + Br (CH3CH2CH2CH2)2CuLi diethyl ether (80%) Dr. Wolf's CHM 201 & 202 14-60

  9. Aryl halides can be used + I (CH3CH2CH2CH2)2CuLi diethyl ether CH2CH2CH2CH3 (75%) Dr. Wolf's CHM 201 & 202 14-61

  10. 14.12An Organozinc Reagent forCyclopropane Synthesis Dr. Wolf's CHM 201 & 202 14-62

  11. Iodomethylzinc iodide formed by reaction of diiodomethane withzinc that has been coated with copper(called zinc-copper couple) reacts with alkenes to form cyclopropanes reaction with alkenes is called theSimmons-Smith reaction Cu CH2I2 + Zn ICH2ZnI Dr. Wolf's CHM 201 & 202 14-63

  12. Example CH2CH3 CH2CH3 CH2I2, Zn/Cu H2C C CH3 diethyl ether CH3 via (79%) I CH2 ZnI Dr. Wolf's CHM 201 & 202 14-64

  13. CH3CH2 CH2CH3 C C H H Stereospecific syn-addition CH2I2, Zn/Cu diethyl ether CH3CH2 CH2CH3 H H Dr. Wolf's CHM 201 & 202 14-65

  14. C C Stereospecific syn-addition CH3CH2 H H CH2CH3 CH2I2, Zn/Cu diethyl ether CH3CH2 H H CH2CH3 Dr. Wolf's CHM 201 & 202 14-66

  15. 14.13Carbenes and Carbenoids Dr. Wolf's CHM 201 & 202 14-67

  16. •• C Br Br Dibromocarbene Carbene name to give to species that contains adivalent carbon (carbon with two bondsand six electrons) (same chemistry with dichlorocarbenes) Carbenes are very reactive; normally cannot be isolated and stored. Are intermediates in certain reactions. Dr. Wolf's CHM 201 & 202 14-68

  17. – •• OC(CH3)3 C • • •• Br – H Br C • • Br Generation of Dibromocarbene Br + Br H Br •• + OC(CH3)3 •• Dr. Wolf's CHM 201 & 202 14-69

  18. – Br Br – Br C • • Br Generation of Dibromocarbene •• C + Br Br Dr. Wolf's CHM 201 & 202 14-70

  19. Carbenes react with alkenesto give cyclopropanes CBr2 is an intermediate stereospecific syn addition Br KOC(CH3)3 + CHBr3 (CH3)3COH Br (75%) Dr. Wolf's CHM 201 & 202 14-71

  20. End of Chapter 14

More Related