Development of the traceless phenylhydrazide linker for solid-phase synthesis.

Area of Science:

• Organic Chemistry
• Polymer Chemistry
• Synthetic Chemistry

Background:

• Solid-phase chemistry relies on linkers for attaching molecules to a solid support.
• Existing linkers can have limitations in terms of cleavage conditions or side reactions.
• Development of new, efficient, and traceless linkers is crucial for advancing synthetic methodologies.

Purpose of the Study:

• To introduce a new oxidatively cleavable traceless linker based on the hydrazide group for solid-phase chemistry.
• To develop novel carboxylic acid resins that prevent imide formation during linker synthesis.
• To demonstrate the utility of the hydrazide linker in various coupling and functionalization reactions.

Main Methods:

• Hydrazide formation between carboxy-functionalized resins and substituted hydrazines.
• Synthesis of new carboxylic acid resins to avoid imide formation.
• Application of polymer-bound acyl hydrazides in Heck, Suzuki, Sonogashira, Stille, Wittig, and Grignard reactions.
• Oxidative cleavage of aryl hydrazides using Cu(II) salts or N-bromosuccinimide (NBS) to form acyl diazenes, followed by nucleophilic attack for product release.

Main Results:

• Successfully synthesized and utilized polymer-bound acyl hydrazides in diverse organic transformations.
• Achieved high yields in the hydrazide formation step due to the development of new carboxylic acid resins.
• Demonstrated selective and traceless release of coupling products under mild conditions and in high purity.
• Established a two-step cleavage protocol using NBS for enhanced control and product isolation.

Conclusions:

• The hydrazide group serves as an effective oxidatively cleavable traceless linker in solid-phase synthesis.
• The developed carboxylic acid resins improve the efficiency of linker introduction.
• This methodology offers a versatile and high-purity approach for synthesizing complex molecules via solid-phase chemistry.