Transition-Metal-Free Homocoupling of 1-Haloalkynes: A Facile Synthesis of Symmetrical 1,3-Diynes

Abstract

Symmetrical 1,3-diyne compounds can be easily synthesized via a transition-metal-free homocoupling reaction of 1-haloalkynes without base and oxidant. The method shows excellent functional group compatibility and high yields.

MnO2‐Promoted Oxidative Radical Sulfonylation of Haloalkynes with Sulfonyl Hydrazides: C(sp)–S Bond Formation towards Alkynyl Sulfones

“…On the basis of these experimental results and previous literature, [10,14,16] we tentatively proposed ap ossible reaction mechanism (Scheme 4). Sulfonyl radical A was generated from sulfonyl hydrazide 4a under oxidative conditions.…”

“…[14] As our recent interest for the synthesis of sulfone derivatives, [15] as well as our continuous effort on exploiting the potentialr eactivities and synthetic applicationso fh aloalkynes, [14] herein, we reportacatalyst-free oxidative radicals ulfonylation of haloalkynes with sulfonyl hydrazides. [16] At the outseto fo ur studies, we investigated this catalystfree oxidativer adical sulfonylation of haloalkynes with bromoalkyne 2a and sulfonyl hydrazide 4a as the startingm aterials in DMA (dimethylacetamide) at 90 8C, using TBHP (tert-butyl hydroperoxide) as an oxidant, which is knownt op romote the generation of sulfonyl radicals from sulfonyl hydrazides ( Table 1, entry 1). Using MnO 2 as the oxidant is very critical for this transformation,d elivering variousa lkynyl sulfones in moderate to good yields.…”

“…[16] To cast some light on the mechanismd etails of this cross-coupling reaction, some control experiments were performed. [16] To cast some light on the mechanismd etails of this cross-coupling reaction, some control experiments were performed.…”

“…Additionally,t he self-coupling products of haloalkynes through C(sp)À C(sp) bond formation weres ignificantly inhibited. [16] At the outseto fo ur studies, we investigated this catalystfree oxidativer adical sulfonylation of haloalkynes with bromoalkyne 2a and sulfonyl hydrazide 4a as the startingm aterials in DMA (dimethylacetamide) at 90 8C, using TBHP (tert-butyl hydroperoxide) as an oxidant, which is knownt op romote the generation of sulfonyl radicals from sulfonyl hydrazides ( Table 1, entry 1). [10] Unfortunately,n one of the desired product 5a was detected by GC-MS or NMR analysis.…”

“…In 2010, we reportedt hat the self-coupling reaction of iodoalkynes could provide the corresponding diynes in high yields. [16] To cast some light on the mechanismd etails of this cross-coupling reaction, some control experiments were performed. First, the competition reactions between self-coupling of iodoalkyne 3a and cross-coupling of iodoalkyne 3a and sulfonyl hydrazide 4a were conducted at different reactiont emperatures.…”