The document discusses the disconnection approach in organic synthesis, focusing on synthesizing alcohols and alkenes through C-C disconnections. It outlines two paths for disconnection, noting the practical benefits of each and the methodologies required to achieve high yields. Additionally, it covers the synthesis of alkenes via elimination reactions and the Wittig reaction, highlighting their importance in the creation of various organic compounds.

1. Organic Synthesis:
The Disconnection Approach
One Group C-C Disconnection of
Alcohol and Alkene
Rabia Aziz
BS-IV Organic Chemistry
VIII Semester
Jinnah University For Women

2. One Functional Group
Analysis
Synthesis (path a)
Disconnection close to the functional
group (path a) leads to substrates (SE)
that are readily available. Moreover,
reconnecting these reagents leads
directly to the desired TM in high yield
using well-known methodologies.
Disconnection via path b also leads to
readily accessible substrates. However,
their reconnection to furnish the TM
requires more steps and involves two
critical reaction attributes: quantitative
formation of the enolate ion and control
of its monoalkylation by ethyl bromide.

3. Synthesis of Alcohol
Alcohols have wide applicability in our daily life. They are
useful as synthetic intermediates, cleansers, cosmetics,
fuels, alcoholic beverages, etc. The synthetic and
retrosynthetic analysis of alcoholic compounds are required
for their utility.

4. Synthesis of
alcoholic compounds
by 1,1 C-C
disconnections:
2-methyl-2-propanol
• Retrosynthetic Analysis
• Synthesis

5. 1. Synthesis of branched side chain
alcohol
• 2,3-dimethylbutan-2-ol
Retrosynthetic analysis
Synthesis

6. 2. Synthesis of unbranched side chain
alcohol
• 2-methylpentan-2-ol
Retrosynthetic analysis
Synthesis:

7. Synthesis of alcoholic compounds by
1,2 C-C disconnections:

8. 1-phenyl-2-butanol
• Retrosynthetic analysis
• Synthesis

9. COMPOUNDS DERIVED FROM
ALCOHOLS

10. Alkene Synthesis

11. 1. Synthesis of Alkenes by Elimination
Reactions
• Alkenes can be made by the dehydration of
alcohols 2, usually under acidic conditions.
• This route is particularly good for cyclic alkenes 3
• The same alkene is formed from 2 regardless of
which side eliminates but 4 gives a 76% yield of
an 80:20 mixture of 5and 6.

12. • When Zimmermann and Keck wished to study
the photochemistry of a series of alkenes of
the general structure 7
• They used the Grignard method and
dehydrated 8 with POCI3 in pyridine.

13. • Eliminations on alkyl halides done by the E2
mechanism with a strong hindered base to
avoid SN2 reactions.
• This approach is good for terminal alkenes 10
as the elimination is successful on primary
halides.

14. 2. Alkene Synthesis by the Wittig
Reaction
Triphenyl phosphine, reacts with an alkyl halide in an SN2 reaction to
give a phos-phonium salt 18. Treatment with base, gives the
phosphoniumylid 19.
The carbanion end of the ylid adds to the aldehyde 22 and the
'betaine' then cyclises 23 to the four-membered ring which frag-
ments to give the products 24. So the Z-alkene 20 is formed from
the cis oxaphosphetane 24.

15. 1.
2.

16. Application of Wittig Reaction
Synthesis of leukotriene antagonists
The 'optical brightener' Palanil 50—it makes your clothes look 'whiter than white' and
your T-shirts fluoresce in UV light