Dihydrothiophenes, part VIII. 2-Carbomethoxy-1,3-butadiene: a convenient synthesis of a stable precursor and a survey of its Diels-Alder reactions

Synthetic Studies of Sesquiterpenes with the Dunniane Skeleton

“…Phenyl vinyl sulfones have been used as a convenient terminal olefin equivalent in the DAR with isoprene (7) and other dienes because the sulfonyl group can be easily removed reductively. [8] Nevertheless, in our approach the regiochemical outcome of the cycloaddition of 9 to 7 or 2-methoxycarbonyl-1,3-butadiene [9] (8) was uncertain and should be investigated. On the other hand, the use of dienamines as Diels-Alder dienes is well documented and it has been shown that they react readily with methyl acrylate (10) in a highly regioselective manner to afford cycloadducts with the appropriate regiochemistry for our synthetic purposes.…”

Permuting Diels–Alder and Robinson annulation stereopatterns

“…35 In this context, C 3 of the C 3 –C 4 iso-DA pattern carries a carboxyl group. One might well have considered synthesizing cosmosoic acid by a Diels-Alder reaction of diene 43 36 with the generic dienophile 44 , followed by isomerization of 45 . To us, it seemed that such a program presented unlikely prospects for success.…”

Michael Reaction of Nitroalkanes with β‐Nitroacrylates under a Solid Promoter: Advanced Regio‐ and Diastereoselective Synthesis of Nitro‐Functionalized α,β‐Unsaturated Esters and 1,3‐Butadiene‐2‐carboxylates

“…[17] 1,3-Butadiene-2-carboxylates 7 are a very important class of molecules since they have been throughly studied in recent years as potential starting materials for organic synthesis, in particular for various [4 + 2] cycloadditions, and a number of these compounds have proven to be valuable precursors for functionalized alkyl 1-cyclohexene-1-carboxylates, [18][19][20][21][22] naturally occurring cyclopentanoid terpenic acids, [23] biologically important litsenolides, [24] and a-alkylidenebutyrolactone natural products. [25] Moreover, our procedure can be applied to a new, efficient preparation of valproic acid (VPA) 9 and its main metabolite…”