Traceless Protection for More Broadly Applicable Olefin Metathesis

Area of Science:

• Organic Chemistry
• Catalysis
• Synthetic Methodology

Background:

• Olefin metathesis is a powerful tool for C=C bond formation.
• Kinetically controlled metathesis often requires protection of sensitive functional groups.
• Expanding the scope of metathesis to include functionalized substrates remains a challenge.

Purpose of the Study:

• To develop a simple and efficient in situ protection/deprotection strategy for olefin metathesis.
• To broaden the substrate scope of kinetically controlled Z- and E-selective olefin metathesis.
• To prepare stereochemically defined alkenes bearing hydroxy or carboxylic acid groups.

Main Methods:

• Treatment of functionalized olefins with HB(pin) or HB(trip)2 for in situ protection.
• Utilizing sensitive Mo- or Ru-based metathesis catalysts.
• Employing routine workup for quantitative deprotection.
• Using HB(pin) to remove residual water and enhance efficiency.

Main Results:

• Successful preparation of Z- and E-alkenyl halides, boronates, and Z-trifluoromethyl-substituted alkenes.
• High yields (51-97%) and excellent stereoselectivity (>98%) achieved.
• Demonstrated applicability to substrates with hydroxy or carboxylic acid groups.
• Enhanced reaction efficiency by using HB(pin) as a water scavenger.

Conclusions:

• The developed in situ protection/deprotection strategy significantly expands the utility of olefin metathesis.
• This method offers a simple, efficient, and highly selective route to valuable functionalized alkenes.
• The strategy is robust and applicable to a wide range of substrates, improving overall reaction outcomes.