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3.10.2.2 Wagner–Meerwein Rearrangement

DOI: 10.1055/sos-SD-203-00270

Jautze, S.; Peters, R.Science of Synthesis: Stereoselective Synthesis, (20113462.

The catalytic enantioselective WagnerMeerwein rearrangement of allenyl-substituted cyclobutanols 57, using a rhodium-based catalyst with chiral ligand 58, provides a general method for the preparation of highly substituted, enantioenriched cyclopentanones 60 with an O-substituted quaternary stereocenter at the α-position relative to the generated carbonyl group (Scheme 16).[‌50‌,‌51‌] The ether substituent (R1) has only a marginal effect on the enantioselectivity; however, substrates containing substituents at the 3-position of the cyclobutane core (R2/R3) usually require higher reaction temperatures in combination with a modified ligand 59 in order to provide high yields and good enantiomeric excesses. Importantly, diastereomerically enriched cyclobutanes (with R2 R3) give products with good diastereo- and enantioselectivities. In this case, the two bonds that can undergo migration are diastereotopic and, as a result, two stereocenters are generated.

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