A Novel Synthesis of 1,3-Oxazine-2,4-diones via a Simple and Efficient Reaction of CO2 with 2,3-Allenamides
摘要:
A simple and efficient reaction of CO2 with 2,3-allenamides under mild conditions (CO2 balloon without any metal catalyst in the presence of K2CO3 or Cs2CO3) leads to an efficient synthesis of 1,3-oxazine-2,4-diones. The high reactivity of the allene moiety is crucial for the success of this transformation since the corresponding reaction of alpha,beta-unsaturated alkenamides or alkynamides does not occur.
Diastereoselective additions of allenylstannanes to aldehydes
摘要:
The allenylstannane 4 undergoes highly syn selective additions to alpha-branched aldehydes 8b and 8c in the presence of BF3.OEt2. With the beta-alkoxy aldehyde 21, Cram-Felkin addition results with BF3.Oet2 as the Lewis acid, whereas MgBr2 leads to chelation-controlled addition.
Diastereoselective and Enantioselective Synthesis of Homopropargyl and Allenylcarbinols from Nonracemic Propargyl Mesylates via the Derived Allenyl and Propargyl Trichlorosilanes