Convenient Stereoselective Syntheses of (6E)- and (6Z)-5,6-Dimethyl-8-silyl-octenals

Doubly Diastereocontrolled Cyclization Based on Intramolecular Conjugate Addition Reactions Involving an Allylic Radical and an Anion

“…Compounds 13 , both in ( E ) and ( Z ) forms, and 14 with ( E ) configuration were synthesized stereoselectively as shown in Scheme . First, ( E ) and ( Z ) side chain synthons 8a and 8b were prepared according to the previously reported method for the stereodivergent synthesis of trisubstituted olefines …”

“…First, (E) and (Z) side chain synthons 8a and 8b were prepared according to the previously reported method for the stereodivergent synthesis of trisubstituted olefines. 13 This time, in the alkylation of enol phosphates 18, the reaction condition was improved in such a way that the reagent and the catalyst were used in fairly less amounts than those reported before. For the (E) series, the stereoselectivity was >99% in both phosphorylation and alkylation steps, while in the case of the (Z) series isomerization of a minor degree occurred in the latter reaction to afford the product 19b with a purity ratio of 96:4.…”

Transition metal-catalysed cross-coupling reactions of P-activated enols

“…75 In spite of this, substitution of the phosphate has been used to prepare alternative organometallic reagents that can allow greater substrate scope in the subsequent crosscoupling reaction. In this respect conversion to vinyl stannanes, boronic acids and silane have been described (Scheme 22c-e) 49,[95][96][97] As with many of these studies, most examples describe the use of cyclic substrates but in one of the first examples of this approach Oshima described the conversion of simple ketone enolates to the corresponding vinyl silanes. Moreover, the stereochemical control in this reaction was excellent with the vinyl silanes 173 and 175 being produced in >95% de from the corresponding vinyl phosphates 172 and 174, respectively (Scheme 22e).…”

“…Moreover, the stereochemical control in this reaction was excellent with the vinyl silanes 173 and 175 being produced in >95% de from the corresponding vinyl phosphates 172 and 174, respectively (Scheme 22e). 96,97…”

Nickel-Catalyzed Cross-Coupling of Dienyl Phosphates with Grignard Reagents in the Synthesis of 2-Substituted 1,3-Dienes

“…Nickel- and palladium-catalyzed cross-couplings between organic halides and organometallic reagents are well-known in the literature . Couplings of organic phosphates have been reported with Grignard reagents, organomanganese reagents, and organoaluminum reagents 4c, with nickel or palladium catalysis. However, little attention has been paid to the synthesis of substituted dienes via these methods.…”