We next aimed to evaluate the scope of alkyl halides
1 (
Scheme 2). Surprisingly, alkyl iodide, 3-phenylpropyl iodide
1b, was lower reactive for furnishing
3aa in 20% yield, attributing to readily decomposition of the C—I bonds. Using lower reactive 3-phenylpropyl chloride
1c failed to construct
3aa. Strikingly, a wide range of functionalized alkyl bromides
1d-aq accommodated to this umpolung C—S radical reductive cross coupling (
3da-aqa). For example, functionalized propyl bromides
1d-g afforded
3da-ga, respectively, in 70%–99% yields where a functionality, such as 4-ClC
6H
4, CN, CO
2Et, and 4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl, at the position γ to the bromide atom was intact. This optimal conditions were compatible with (2-bromoethoxy)(
tert-butyl)-dimethylsilane
1), producing the high useful silyl-substituted product 3 ha in 80% yield. Using (3-bromoprop-1-en-1-yl)benzene
1i, an alkene, furnished cinnamyl(phenyl)sulfane
3ia in good yield. The linear alkyl chains containing one to six carbon atoms were competent to the coupling, and several functional groups, including aryl, F, OH and Cl, were tolerated (
3ja-sa). Alkyl bromides
1t-w with steric hindrance were suitable substates (
3ta-wa). Broad secondary and tertiary alkyl bromides, including (1-bromoethyl)benzene
1x,
α-bromoketones (
1y,
1ad), four- to seven-membered cycloalkyl bromides (
1z-ac),
α-bromo ester (
1ae) and
α-bromo amide (
1af), were subject to the coupling, furnishing the corresponding secondary and tertiary alkyl sulfanes
3xa-aca in high to quantitative yields. Interestingly, dual umpolung C—S radical reductive cross couplings of alkyl dibromides
1ag-ak executed successfully to access disulfanes
3aga-aka, which highlights the applicability of our protocol in organic and material synthesis. A number of natural product- or bioactive molecule-based alkyl bromides
1al-aq, such as L-alaninate derivative [
69], telmisartan derivative [
70], cholesterol derivative [
71], 4-androstene-3,17-dione derivative [
72], estrone derivative [
73] and estradiol pentanoate derivative [
74], exposed to the optimized conditions resulted in selective transformation of the C(sp
3)—Br bonds to the C(sp
3)—S bonds to produce highly valuable complex products
3ala-ana,
3aob,
3apa-aqa, thus providing a powerful route to selective late stage modification of complex bioactive substrates with multiple potential sites of reaction. Unfortunately, aryl halides, such as bromobenzene and iodobenezen, had no reactivity for the reaction.