The vinylation of glycosyl-DHPs 6b-d was then examined, and low diastereoselectivity was observed with mannosyl DHP 6b and xylosyl DHP 6c. Ribosyl DHP 6d proved to be a better substrate, delivering product 7d in good yield and 15:1 dr. The high stereoselectivities observed with substrates 6a and 6d are likely due to the steric interactions induced by the adjacent acetonide, and the results are consistent with Nakamura's and Molander's transition metal-catalyzed radical C-arylations of glycosyl donors. Substrate 6d was employed in the VBX scope, and the desired products 7e-7j were obtained in 50-73% yield with good to excellent diastereoselectivities and complete (E)-selectivity using both electron rich and electron poor (E)-VBXs. The structure of 7j (major diastereomer) was confirmed by X-ray crystallographic analysis. Trisubstituted heteroatom-VBX were next explored, and the desired C-vinyl glycosides 7k and 7l could indeed be synthesized with excellent diastereoselectivity and complete (Z)-selectivity. The applicability of the methodology was briefly explored with EBX reagents and gratifyingly, the reaction conditions worked equally well for alkynylations to afford 8a and 8b in 91% and 95% yield, respectively with excellent dr (Scheme 4). Subsequent mechanistic studies with substrate 1i and VBX 2a supported our hypothesis of a photocatalytic radical coupling. Control experiments in the absence of 4CzPN or LED light resulted in no product formation. Furthermore, reactions in the presence of TEMPO were inhibited, and the alkyl-TEMPO adduct was detected by HRMS. Furthermore, vinylation of bridgehead-DHP 1x delivered a 1:1 mixture of norbornenyl and nortricyclyl products 3x and 3x', indicating a radical equilibrium during the coupling process (Scheme 5a). A reaction of 1i with the deuterated VBX 2a-D delivered product 3o-D in 60% isolated yield as the only regio-and stereoisomer, indicating that no rearrangement takes place during the vinylation (Scheme 5b).