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- 18. The acetal / ketals protective group is introduced by treating the carbonyl compounds with an alcohol. an ortho-ester. or a diol in the presence of a Lewis acid as catalyst. Acetals / ketals are stable to strong aqueous bases. nucleophilic reducing agents. organometallic reagents. oxidation under non-acidic conditions. Na or Li/NH3 reductions. Acetals / ketals are cleaved by acid …
- PROTECTIVE GROUPS IN ORGANIC SYNTHESIS. MOM-OR Methoxymethyl ether. MOM ether H2O: pH 12. 100°C Bases: LDA NEt3. Py t-BuOK Others: DCC SOCl2 Nucleophiles: RLi RMgX RCuLi Enolates NH3. RNH2 NaOCH3 Electrophiles: RCOCl RCHO CH3I Others: :CCl2 Bu3SnH Reduction: H2 / Ni H2 / Rh Zn / HCl Na / NH3 LiAlH4 …
- Benzyl ethers as protecting groups for alcohols + pyridine H 2 /Pd Benzyl ether is stable to base. mild acid. oxidation & reduction Protection Deprotection 15. t- Butyl ethers as protecting groups for alcohols + or H + Protection H 3 O + Deprotection t-Butyl ether is stable to base. mild acid. oxidation & reduction 16. PROTECTION OF ALCOHOLS 3.
- Protecting Groups in Organic Synthesis What is a protecting group? A protecting group (PG) is a molecular framework that is introduced onto a specific functional group (FG) in a poly-functional molecule to block its reactivity under reaction conditions needed to make modifications elsewhere in …
- Why difficult to couple alkyl halides Protecting groups (PG) in organic synthesis (McM 17. 9) Examples Protection of ROH (McM 17. 9) Other ex. of ROH protecting groups (not mentioned in McM) esters also for prot. of acids Protection of aldehydes / ketones (McM 19. 11) Two extra steps The protecting group …
- Other protecting group: Boc Amine PGs Introduction Cbz 2 O. Cbz‐Cl Alloc 2 O. Alloc‐Cl ivDde‐OH Removal H 2 Pd (PPh 3). PhSiH 3 2% N 2 H 4 Stable Basic and Acidic conditions Basic and Acidic conditions Basic and Acidic conditions. Hydrogenation Orthogonal Boc. Fmoc. Trt Boc. Fmoc. Trt Boc. Fmoc. Z. Trt. Alloc 4. For α‐carboxylic acids. Aspartic and Glutamic Acid Carboxylic acid PGs . . .
- The Role of Protective Groups in Organic Synthesis 1 2. Protection for the Hydroxyl Group. Including 1. 2- and 1. 3-Diols 16 Ethers. 24 Esters. 222 Protection for 1. 2- and 1. 3-Diols. 299 3.
- Protecting Groups in Organic Synthesis-1 Ready Protecting groups are a sad fact of synthetic chemistry They are usually needed. but rarely desired Many syntheses have stalled because of trouble putting on or removing protecting groups 4 basic questions to address when choosing a P. G. : 1.
- The Fourth Edition of Greene’s Protective Groups in Organic Synthesis continues to be an indispensable reference for controlling the reactivity of the most common functional groups during a synthetic sequence. This new edition incorporates the significant developments in the field since publication of the third edition in 1998. including. . . …
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