84864-39-1Relevant academic research and scientific papers
A new highly efficient three-component domino Heck-Diels-Alder reaction with bicyclopropylidene: Rapid access to spiro[2.5]oct-4-ene derivatives
Nueske, Hanno,Braese, Stefan,Kozhushkov, Sergei I.,Noltemeyer, Mathias,Es-Sayed, Mazen,De Meijere, Armin
, p. 2350 - 2369 (2002)
Bicyclopropylidene (1) was found to surpass even methyl acrylate (17a) in its rate of undergoing carbopalladation with aryl- or alkenylpalladium species, leading to substituted allylidenecyclopropanes 5, 7 and 10, mostly in high yields (37-78%). These dienes and cross-conjugated trienes react in a Diels-Alder mode with dienophiles to give spiro[2.5]octenes 18a-Ph, 18b-Ph and 18a-Vin, respectively, in good yields (89, 69 and 65 %). The overall transformation can be achieved as a one-pot three-component reaction with a variety of dienophiles to furnish the domino Heck-Diels-Alder products 18 regioselectively in most cases in good to very high yields (49-100%). The reaction of 1 with iodobenzene (2-Ph) and 17a gave 18a-Ph in virtually quantitative yield - also on a gram scale - using only 1 mol% of catalyst, and even bromobenzene (22) gave 18a-Ph in 59% yield. Bicyclopropylidene (1), in the presence of palladium acetate/triphenylphosphane underwent rearrangement to allylidenecyclopropane (5-H), which in turn dimerized (73%) in the absence of other reaction partners, or could be trapped by diethyl fumarate (17c) to give the Diels-Alder adduct 18c-H in 45% yield. The coupling of oligoiodobenzenes with 1 and subsequent cyclo-addition could be extended to a multicomponent reaction. In this way, 1,4-diiodobenzene (37), 1 and an alkyl acrylate gave the products 38 of a twofold Heck-Diels-Alder reaction in up to 87% yield, 1,3,5-triiodobenzene (39) reacted in up to 72% yield and ultimately 1,2,4,5-tetraiodobenzene (41) gave the fourfold domino Heck-Diels-Alder product 42 in 47 % isolated yield, in a single operation in which 12 new carbon-carbon bonds were formed.
