(E)-.beta.,.gamma.-Unsaturated esters from 9-alkenyl-9-BBN and ethyl (dimethylsulfuranylidene)acetate

Asymmetric Synthesis of α‐Substituted Allyl Boranes and Their Application in the Synthesis of Iso‐agatharesinol

“…However, in the reaction of nonsymmetrical boranes with sulfur ylides, issues of migration ability of the different groups have to be addressed. [8] Although the vinyl group is expected to be a better migrating group than the boracycle, [9] the outcome was not clear, as we had already experienced surprises in the reaction of B-phenyl-9-BBN with the ylide derived from 1, in which we found competing migration of the boracycle. [10] In the event, reaction of the ylide derived from 1 with vinylborane 2 a at À100 8C followed by addition of PhCHO at the same temperature furnished the homoallylic alcohol 5 a in 96 % yield as a single diastereomer with high Z selectivity (procedure A, Scheme 1).…”

Pd-Catalyzed Cross-Coupling of Potassium Alkenyltrifluoroborates with 2-Chloroacetates and 2-Chloroacetamides

“…3 Another common method is the deprotonation/reprotonation of α,β-unsaturated carbonyl compounds. Alternative approaches include the reaction of alkenyl-9-BBN compounds with α-halo carbanions generated from ethyl bromoacetate 4 or ethyl (dimethylsulfuranylidene) acetate, 5 cross-metathesis of allyl halides with olefins bearing amides 6 or by a sequential elimination-reduction process of α-halo-β-hydroxy-γ,δ-unsaturated esters promoted by SmI 2 . 7 Radical addition of alkenylindiums to α-halo carbonyl compounds 8 and Ni-catalyzed enantioselective addition of alkenylzirconium reagents to α-bromo esters and ketones 9 have emerged as more recent advances in the synthesis of β,γ-unsaturated carbonyl moieties.…”

Stereoselective Syntheses of β,γ-Unsaturated Esters and γ-Lactones: 1-(Benzotriazol-1-yl)-3-(diphenylphosphoryl)-1-ethoxy-1-propene, a Protected CCH2CO2Et Synthon Equivalent

“…Treatment of 4a − c with TsOH·H 2 O−EtOH readily afforded the β,γ-unsaturated esters 2a − c in 88−95% yields. β,γ-Unsaturated esters have previously been prepared by (i) reaction of organoboranes with either α,β-unsaturated γ-bromo esters or ethyl (dimethylsulfuranylidene)acetate, (ii) electrocatalyzed carboxylation of allyl chlorides, (iii) carbonylation of (η 3 -allyl)Fe(CO) 3 (NO), (iv) palladium-catalyzed carbonylation of allyl phosphates, acetates, or halides, (v) palladium- and nickel-catalyzed coupling of vinyl bromides with Reformasky reagents, (vi) isomerization of α,β-unsaturated esters, − and (vii) treatment of α,β-unsaturated α-bromo esters with dialkyl phosphonates . No previous report has been found for the preparation of β,γ-unsaturated esters via formation of the CC double bond.…”