Controlling Factors for C−H Functionalization versus Cyclopropanation of Dihydronaphthalenes

Rhodium(II)-catalyzed reactions of vinyldiazoacetates with dihydronaphthalenes were systematically studied. These substrates underwent cyclopropanantion and/or the combined C−H activation/Cope rearrangement in good overall yield and with good diastereo- and enantiocontrol. The selectivity of these reactions was profoundly influenced by the nature of the chiral catalyst, the vinyldiazoacetate, and the dihydronaphthalene. The best combinations for achieving the highest selectivity in the cyclopropanation and the combined C−H activation/Cope rearrangement of 1,2-dihydronaphthalenes are methyl 2-diazopent-3-enoate (2a)/Rh2(S-DOSP)4 and methyl 3-(tert-butyldimethylsilyloxy)-2-diazopent-3-enoate (2b)/Rh2(S-PTAD)4. These combinations are very effective at enantiodivergent reactions of 1-methyl-1,2-dihydronaphthalenes.