Enantioselective Rh-Catalyzed Carboacylation of C═N Bonds via C–C Activation of Benzocyclobutenones

Abstract

Herein we describe the first enantioselective Rh-catalyzed carboacylation of oximes (imines) via C–C activation. In this transformation, the benzocyclobutenone C1–C2 bond is selectively activated by a low valent rhodium catalyst and subsequently the resulting two Rh–C bonds add across a C=N bond, which provides a unique approach to access chiral lactams. A range of polycyclic nitrogen-containing scaffolds were obtained in good yields with excellent enantioselectivity. Further derivatization of the lactam products led to a rapid entry to various novel fused heterocycles.

“Cut and Sew” Transformations via Transition-Metal-Catalyzed Carbon–Carbon Bond Activation

“…The intramolecular carboacylation of oxime ethers ( 96 ) with benzocyclobutenones provides an efficient entry to fused tetrahydroisoquinoline rings (Scheme 61). 78 High levels of enantioselectivity were maintained even using substrates as a mixture of E / Z oxime isomers. Subsequent derivatization of the lactams was possible through N -arylation and alkylation upon cleavage of the N–OMe bond (not shown).…”

Methylenecyclopropane Annulation by Manganese(I)‐Catalyzed Stereoselective C−H/C−C Activation

“…Theu nique performance of the manganese(I) catalysis was reflected by attempted C À H/C À Ca ctivations with either manganese(II) salts or frequently used cobalt, ruthenium, rhodium, and palladium catalysts,all of which fell short in delivering any of the desired product 3aa (entries [6][7][8][9][10][11][12]. Theu nique performance of the manganese(I) catalysis was reflected by attempted C À H/C À Ca ctivations with either manganese(II) salts or frequently used cobalt, ruthenium, rhodium, and palladium catalysts,all of which fell short in delivering any of the desired product 3aa (entries [6][7][8][9][10][11][12].…”

“…[4] In this context, considerable recent advances have been realized with less toxic organometallic manganese(I) catalysis, [5] with key contributions by the groups of Kuninobu, [6] Wang, [7] and Ackermann, [8] among others. [9] As ignificant stimulus in CÀHa ctivation chemistry has very recently been gained by merging CÀHfunctionalization with challenging C À C [10,11] cleavage strategies.I ns pite of these undisputed advances,catalytic [12] C À H/C À Cfunctionalizations continue to be scarce,w ith the reported examples thus far calling for precious rhodium catalyst, [13] and/or activated vinylcyclopropanes. [14] In sharp contrast, we have now uncovered the first base-metal-catalyzed CÀH/CÀC functionalization with synthetically useful methylenecyclopropanes (MCPs), [15] and report our findings herein.…”

Cyclobutenones and Benzocyclobutenones: Versatile Synthons in Organic Synthesis

“…Apart from coupling with nonpolar p bonds in substrates such as alkenes and alkynes,t he Dong group later expanded the "cut and sew" transformation by utilizingm ore polar C=N bonds,f or example, in oximes, as intramolecular coupling partners (Scheme 67). [70] The cationic [{Rh(cod)(CH 3 CN) 2 }]BF 4 was foundt ob et he optimal precatalyst. High enantioselectivity and decent yields were achieved by using ac ombinationo f Scheme60.…”

“…[74] As indicated in Liebeskind's work, [53] the insertion of rhodiumi nto the C1ÀC8 bond of benzocyclobutenones is kinetically favored. In the absence of coordination of unsaturated p moieties, [64][65][66][67][68][69][70] concomitant b-H elimination could occur Scheme67. Enantioselectiverhodium-catalyzed carboacylation of C=Nb onds.SDP = 7,7'-bis(diphenylphosphino)-2,2',3,3'-tetrahydro-1,1'-spirobiindene.…”