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

Abstract

1-(Benzotriazol-1-yl)-3-(diphenylphosphoryl)-1-ethoxy-1-propene (3), prepared from N-(α-ethoxyallyl)benzotriazole (1), underwent selective Horner reactions with aldehydes to give substituted dienes. Subsequent hydrolysis of these intermediates readily produced β,γ-unsaturated esters 2a − c in good yields. Similar reactions with ketones followed by hydrolysis of 10 produced, depending on the conditions, either the corresponding γ,γ-disubstituted β,γ-unsaturated esters 11a − d or γ-lactones 9a − c and 13. A double lithiation process provided β,γ,γ-trisubstituted β,γ-unsaturated esters 15, 18, and β,γ,γ-trisubstituted γ-lactone 14.

A Facile Synthesis of 3-Substituted-2-aminothiophenes and 1,3-Disubstituted-2-methylthiopyrroles

“…Intermediate 2g (Scheme ) was obtained by one-step condensation of acrolein diethyl acetal with benzotriazole in refluxing hexanes for 18 h, followed by purification of the crude product by flash column chromatography which allowed for the separation of the Bt 1 and Bt 2 isomers (for the structures of Bt 1 and Bt 2 , see Scheme ).…”

1,2,3-Triazoles

“…For the derivatives of aldehydes ( 884 , R 2 = H), (E) – (E) stereoselectivity of the elimination is observed. Acidic alcoholysis of dienes 884 affords esters of β,γ-unsaturated carboxylic acids 885 < 1997JOC4131> .

Scheme 145

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Regioselectivity of the Reactions of Heteroatom-Stabilized Allyl Anions with Electrophiles

“…In the aldehyde and ketone cases, Horner reaction occurs to give substituted dienes 817 or 820 . Further acidic treatment of 817 under anhydrous conditions produces β,γ-unsaturated esters 816 , but hydrolysis under aqueous conditions affords γ-lactones 821 (Scheme ) 156 …”