Sulfoximine‐Directed Single and Double <i>ortho</i>‐Lithiation: Stereoselective Rearrangements of <i>o</i>,<i>o</i>′‐Dilithiophenylsulfoximines to <i>o</i>,<i>N</i>‐Dilithiosulfinylanilines through Anionic Fries Rearrangements of <i>o</i>,<i>o</i>′‐Dilithiophenylsulfinamides

Abstract

Abstract Treatment of various phenylsulfoximines with n BuLi (1 equiv.) at –78 °C in THF resulted in single ortho ‐lithiations and gave the corresponding o ‐lithiosulfoximines. According to NMR spectroscopy, the o ‐lithiosulfoximines are generally stable at 0 °C. The o ‐lithiosulfoximines were efficiently trapped through deuteration, alkylation, silylation, and phosphanylation. Treatment of cyclic phenylsulfoximines also containing H atoms at their α‐positions with n BuLi (1 equiv.) at –78 °C furnished the o ‐lithiosulfoximines with high selectivity, whereas similar treatment at –50 °C to room temperature yielded the corresponding α‐lithiosulfoximines. At elevated temperatures, o ‐lithiosulfoximines also possessing α‐H atoms underwent quantitative o ,α‐transmetalation to afford the corresponding α‐lithiosulfoximines. Treatment of α,α‐disubstituted cyclic and α,α,α‐trisubstituted acyclic phenylsulfoximines with n BuLi (2 equiv.) at low temperatures led to double ortho ‐lithiation and furnished the corresponding o , o ′‐dilithiosulfoximines. At elevated temperatures, cyclic o , o ′‐dilithiophenylsulfoximines underwent multi‐step rearrangements with formation of o , N ‐dilithiated benzothiazepine and benzothiazocine S ‐oxide derivatives in high yields. Theacyclic o , o ′‐dilithiophenylsulfoximine underwent a similar rearrangement and gave the corresponding o , N ‐dilithio‐sulfinylaniline derivative. The rearrangements involve 1) elimination of the lithium sulfinamide from the o , o ′‐dilithiosulfoximine, 2) a Li–N addition of the lithium sulfinamide to the o ‐lithiobenzyne, and 3) an anionic Fries rearrangement of the o , o ′‐dilithiophenylsulfinamide. The rearrangements of the o , o ′‐dilithiophenylsulfoximines proceeded with overall retention of configuration at sulfur.