Stereochemistry of addition of organocopper reagents and of the hydride ion to 1-(arylsulfonyl)bicyclo[1.1.0]butanes

Abstract

Addition of methylmagnesium iodide/cuprous iodide or of lithium dimethylcuprate to 2-exo-and 2-endomethyl-1 -(phenylsulfonyl)bicyclo[ 1.1.0]butane and determination of the relative geometry of the methyls in the 2,3-dimethylcyclobutanes obtained allowed us to establish that addition of the methyl group occurred from the endo side of the bicyclic molecule. Similarly, lithium aluminum hydride reduction of 2-exo,3-and 2-endo,3dimethylbicyclobutane was also found to occur by endo-addition of the hydride ion at position 3 of the bicyclic system.

The Julia Reaction

“…For example, primary and secondary a-metalated sulfones add smoothly to formaldehyde [16,17] (Scheme 3.7). Although this approach is quite successful, few examples have hitherto been reported [16][17][18][19][20][21][22][23].…”

“…Since Na 2 O can be considered as a rather poor leaving group, the anionic intermediates 130 may be quenched by a proton source before elimination occurs [118][119][120][121][122]. During a total synthesis of neodolabellenol in 1995, Williams et al [123] took advantage of these considerations and intentionally performed such a desulfonation to complete their synthesis (Scheme 3.26).…”

“…Indeed, when substitution prohibits elimination towards the corresponding vinyl sulfones [122,125,126], as in the case of substrate 172 [127], the reduction promoted by Na(Hg)/MeOH still remains highly efficient (Scheme 3.33).…”

Enantioselective Synthesis of Cyclobutanes via Sequential Rh-catalyzed Bicyclobutanation/Cu-catalyzed Homoconjugate Addition

“…In seminal studies, Gaoni showed that cuprate reagents can add across the central C-C bond of 1-sulfonyl bicyclobutanes. 12 The diastereoselectivity for such processes was variable. Moreover, analogous reactions of other bicyclobutane derivatives were unknown.…”

“…The uncatalyzed addition of PhMgBr in Et 2 O gave only traces of diastereomers 4 upon acidic quench (entry 1). Conditions of Gaoni 12 (CuI in Et 2 O) gave 4 in only 8% yield (entry 2). Neither CuCN nor CuBr•SMe 2 promoted the reaction under similar conditions (entries 3,4).…”