Lithium 3-Lithio-3-tosylalkanoates: .beta.-Acylvinyl Anion Equivalents of .beta.-Lithiated .alpha.,.beta.-Unsaturated Carboxylic Acids
摘要:
The dilithiation of beta-tosylated propanoic, 2-methylpropanoic, and butanoic acid 10 with n-butyllithium at -78 degrees C leads to the corresponding lithium 3-lithio-3-tosylalkanoates 11. They react with different electrophilic reagents (deuterium oxide, iodine, trimethylchlorosilane, alkyl halides, and acyl chlorides) to give the corresponding 3-substituted tosylated alkanoic acids 12. When carbonyl compounds are allowed to react with intermediates 11 followed by in situ lactonization with trifluoracetic anhydride and base-promoted elimination alpha,beta-butenolides are obtained. This methodology is applied to the direct synthesis of the rosefuran lactone precursor 14cg, the O-benzyl derivative of (+/-)-umbelactone (14ch), and (+/-)-andirolactone (14ci). The alkylation and acylation reactions of organolithium compounds 11 followed by esterification with hydrogen chloride in methanol and treatment with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) afford alpha,beta- and/or beta,gamma-unsaturated esters 17 and/or 18 and unsaturated 4-keto esters 19, respectively. The last methodology has been applied to the synthesis of the unsaturated 4-keto ester 19ae precursor of the seco acid of (+/-)-pyrenophorin (22).
The reactivity of the highly functionalized copper, zinc reagents RCu(CN)ZnI toward 1-haloalkynes and acetylenic esters
作者:Ming Chang P. Yeh、Paul Knochel
DOI:10.1016/s0040-4039(01)80511-6
日期:1989.1
The highlyfunctionalizedorganometallics RCu(CN)ZnI 1 react efficiently with 1-haloalkynes providing polyfunctionalized alkynes in high yields. This method has been used to prepare a pheromone of the Amathes c-nigrum in 3 steps and 64% overall yield. The reagents 1 also add in the presence of an excess of Me3SiCl to acetylenic esters to afford polyfunctionalized C—silylated ethylenic esters. In the
<i>anti</i>-Selective synthesis of β-boryl-α-amino acid derivatives by Cu-catalysed borylamination of α,β-unsaturated esters
作者:Soshi Nishino、Yuji Nishii、Koji Hirano
DOI:10.1039/d2sc06003e
日期:——
borylamination of α,β-unsaturated esters with B2pin2 and hydroxylamines has been developed to deliver acyclic β-boryl-α-amino acid derivatives with high anti-diastereoselectivity (up to >99 : 1), which is difficult to obtain by the established methods. A chiral phosphoramidite ligand also successfully induces the enantioselectivity, giving the optically active β-borylated α-aminoacids. The products can be stereospecifically
已开发出铜催化的 α,β-不饱和酯与 B 2 pin 2和羟胺的区域选择性和非对映选择性硼胺化,以提供具有高抗非对映选择性(高达 >99 : 1)的无环 β-硼基-α-氨基酸衍生物),用现有的方法很难得到。手性亚磷酰胺配体也成功地诱导了对映选择性,产生光学活性的β-硼化α-氨基酸。该产品可以立体定向地转化为β-功能化的α-氨基酸,这在药物化学领域具有重要意义。