r in which the copper atom adds to the carbon β of the heteroatom [ 16 – 17 ], whereas an acceptor substituent (XR = SR, SOR, SO 2 R, SiMe 3 , PR 2 , P(O)R 2 , Path A , Scheme 1 ) would preferably give the α-isomer [ 16 – 17 ] (copper geminated to the heteroatom, Scheme 1 ). Although N -substituted alkynes are known to give the β-isomer, we thought that a precomplexation of the organometallic species (i.e., copper) with a polar functional group in the vicinity of the reactive center should be able to reverse the regioselectivity of the carbometallation, as we have shown for the carbocupration of ethynyl carbamate (XR = OCONR 2 , Path C , Scheme 1 ) [ 24 ]. Scheme 1. Open in a new tab Possible regioisomers obtained in the carbocupration reaction of α-heterosubstituted acetylenes 1 . Herein we describe our results for the regio- and stereoselective carbometallation reaction of N- alkynylsulfonyl amides and various N -alkynylcarbamates [ 25 ]. Results and Discussion Carbocupration of sulfonyl-substituted ynamides Our initial experiments were directed towards the carbometallation reaction of N -alkynylsulfonylamides, as the coordination of the organometallic species by the sulfonyl group should control the regioselectivity of the carbometallation reaction in favor of the α-isomer. When 2 was added to an organocopper (easily prepared by the addition of one equivalent of R 2 MgBr to one equivalent of CuBr in Et 2 O at −50 °C), the carbometalated products 3 were obtained in good isolated yields after hydrolysis ( Scheme 2 , conditions A and Table 1 , entries 1–3). Some of these results were published as a preliminary note in [ 25 ]. Scheme 2. Open in a new tab Regioselective carbometallation of N -alkynylsulfonamide 2 . Table 1. Carbometallation reactions of the N -alkynylsulfonamide 2 . Entry Conditions a R 2 E–X Product Yield (%) b 1 A n -Bu H 3 O + 3a 93 2 A Me H 3 O + 3b 30 3 A n -Bu AllylBr 3c 50 4 B n -Bu H 3 O + 3a 90 5 B Me H 3 O + 3b 70 Open in a new tab a Conditi