Synthesis of Simple Diynals, Diynones, Their Hydrazones, and Diazo Compounds: Precursors to a Family of Dialkynyl Carbenes (R¹—C≡C—C̈—C≡C—R²)

Abstract

A variety of substituted pentadiynols, -diynals, and -diynones have been prepared en route to precursors to dialkynyl carbenes (R(1)-C≡C-C-C≡C-R(2)). In light of the marginal stability associated with these simple systems, several strategies were required to assemble the carbon backbones. The requisite five-carbon skeletons were prepared using 4 + 1, 3 + 2, 2 + 2 + 1, and 2 + 1 + 1 + 1 coupling methodologies. The Dess-Martin periodinane serves as an excellent method for the oxidation of pentadiynols to diynals and diynones, although many of the oxidized products are sufficiently reactive that they were not isolated; rather, they were generated in situ and intercepted with nucleophiles such as tosylhydrazide or trisylhydrazide. The hydrazone derivatives are generally reliable precursors to diazo compounds and carbenes, although cyclization of the hydrazone to afford a pyrazole can be a complicating factor in certain instances.

Cascade Reactions Forming Highly Substituted, Conjugated Phospholes and 1,2‐Oxaphospholes

“…[7] In contrast to the plethora of synthetic procedures that are available for the preparation of pure hydrocarbons, the synthetic arsenal for the construction of I-III is limited. The Li salt of 1 [9] is added to 1,5-bis(TES)-penta-1,4-diyne-3-one (2 a, TES = SiEt 3 ), [13,14] resulting in a red solution from which a bright red product 3 can be isolated in 57 % yield after silica gel chromatography. Whereas traditional phosphonium ylides react with diacetylenic ketones exclusively in a 1,2-addition, which makes Wittigtype reactions a reliable tool for the preparation of 1,1diethynylethenes, [11,12] herein we demonstrate that a pWH reagent 1 exhibits a completely different reactivity.…”

“…The Li salt of 1 [9] is added to 1,5-bis(TES)-penta-1,4-diyne-3-one (2 a, TES = SiEt 3 ), [13,14] resulting in a red solution from which a bright red product 3 can be isolated in 57 % yield after silica gel chromatography. The Li salt of 1 [9] is added to 1,5-bis(TES)-penta-1,4-diyne-3-one (2 a, TES = SiEt 3 ), [13,14] resulting in a red solution from which a bright red product 3 can be isolated in 57 % yield after silica gel chromatography.…”

“…Reaction of bis(phenylacetylene)-substituted ketone 2 b [13,14] with the same pWH reagent 1 under identical conditions generates an orange crystalline solid 4 in 38 % yield of isolated product. Compound 4 is structurally fundamentally different from 3, with a mass spectrum that shows a highest weight molecular ion (m/z = 1709.01456, C 64 H 52 O 18 P 4 W 2 + Ag) that corresponds exactly to the mass of two molecules of 1 plus two molecules of ketone 2 b.…”

Multicomponent Double Diels–Alder/Nazarov Tandem Cyclization of Symmetric Cross‐Conjugated Diynones to Generate [6‐5‐6] Tricyclic Products

“…We began by examining a variety of common Lewis acids for the Diels–Alder reaction of bis(trimethylsilyl)diynone 1 a and 2,3‐dimethyl‐1,3‐butadiene 2 a (Table ). We were predominately interested in determining efficacious Lewis acids for the direct conversion of 1 a to 5 a in a single reaction pot, presumably through intermediates 3 a and 4 a .…”

Versatile Bisethynyl[60]fulleropyrrolidine Scaffolds for Mimicking Artificial Light‐Harvesting Photoreaction Centers

“…However, when using Electronic effects: We then investigated the formation and reactivity of azomethine ylides using ketones that bore different electron-donating (ED) or electron-withdrawing (EW) groups (19-21; Scheme 1 and Table 2). 1,5-Bis(phenyl)penta-1,4-diyn-3-one (19) and 1,5-bis[p-N,N-di(n-hexyl)anilino]penta-1,4-diyn-3-one (20) were prepared according to the reported procedures, [50,51] whereas 1,5-bistrifluormethylpenta-1,4-diyn-3-one (21) was synthesized by following the route displayed in Scheme 2. Starting from commercially available prop-2-yn-1-ol, Sonogashira-type cross-coupling with 1-bromo-4-(trifluoromethyl)benzene (22) (Table 2, entry a), no product formation was detected when the reaction was performed in ODCB (Table 2, entry b) despite the full conversion of the ketone.…”