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Asymmetric 1,3‐Dipolar Cycloadditions of 2‐Diazocyclohexane‐1,3‐diones and Alkyl Diazopyruvates
Author(s) -
Müller Paul,
Chappellet Sabrina
Publication year - 2005
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.200590071
Subject(s) - chemistry , ylide , cycloaddition , diazo , enantioselective synthesis , catalysis , carbene , medicinal chemistry , enol , 1,3 dipolar cycloaddition , adduct , organic chemistry
The 1,3‐dipolar cycloaddition reactions of 2‐diazocyclohexane‐1,3‐dione ( 7a ; Table 1 ) and of alkyl diazopyruvates ( 11a – e ; Table 3 ) to 2,3‐dihydrofuran and other enol ethers have been investigated in the presence of chiral transition metal catalysts. With Rh II catalysts, the cycloadditions were not enantioselective, but those catalyzed by [Ru II Cl 2 ( 1a )] and [Ru II Cl 2 ( 1b )] proceeded with enantioselectivities of up to 58% and 74% ee, respectively, when diazopyruvates 11 were used as substrates. The phenyliodonium ylide 7c yielded the adduct 8a in lower yield and poorer selectivity than the corresponding diazo precursor 7a ( Table 2 ) upon decomposition with [Ru(pybox)] catalysts. This suggests that ylide decomposition by Ru II catalysts, contrary to that of the corresponding diazo precursors, does not lead to Ru‐carbene complexes as reactive intermediates. Our method represents the first reproducible, enantioselective 1,3‐cycloaddition of these types of substrates.