The synthesis of olefins and ketones from carbonyl compounds and carbanions alpha to silicon

Aza-Peterson Olefinations: Rapid Synthesis of (E)-Alkenes

An aza-Peterson olefination methodology to access 1,3-dienes and stilbene derivatives from the corresponding allyl- or benzyltrimethylsilane is described. Silanes can be deprotonated using Schlosser’s base and added to N-phenyl imines or ketones to directly give the desired products in high yields.

Stereocontrolled Total Synthesis of Tetrodotoxin from myo-Inositol and D-Glucose by Three Routes: Aspects for Constructing Complex Multi-Functionalized Cyclitols with Branched-Chain Structures

This report describes the stereocontrolled total synthesis of the multi-functionalized cyclitol derivative, tetrodotoxin, containing eight asymmetric carbons and different types of branched-chains, from myo-inositol and D-glucose using three different methods. The tetrodotoxin derivatives possess a relatively small molecular weight but unique structural and chemical properties. Selection of the appropriate synthetic method may be useful not only for compounds related to TTX (including related derivatives), but also for other highly complex multi-functionalized cyclitols containing branched-chains.

Stereocontrolled Total Synthesis of Tetrodotoxin from myo-Inositol and D-Glucose by Three Routes: Aspects for Constructing Complex Multi-Functionalized Cyclitols with Branched-Chain Structures

This report describes the stereocontrolled total synthesis of the multi-functionalized cyclitol derivative tetrodotoxin containing eight asymmetric carbons and different types of branched-chains from myo-inositol and D-glucose using three different methods. The tetrodotoxin derivatives possess a relatively small molecular weight but unique structural and chemical properties. Selection of the appropriate synthetic method may be useful not only for compounds related to TTX (including related derivatives) but also for other highly complex multi-functionalized cyclitols containing branched-chains.

Concise, asymmetric total synthesis of spirotryprostatin A

[structure: see text] The structurally intriguing cell-cycle inhibitor spirotryprostatin A has been synthesized utilizing an azomethine ylide dipolar cycloaddition reaction as the key step. This pentacyclic alkaloid contains a prenylated tryptophan-derived oxindole moiety that has been created in a regiocontrolled and stereocontrolled manner in a single step.

Reactions of gem-dibromo compounds with trialkylmagnesate reagents to yield alkylated organomagnesium compounds

The reaction of gem-dibromocyclopropanes 5 with nBu(3)MgLi affords butylated cyclopropylmagnesium species that can be trapped with various electrophiles. The reaction of dibromomethylsilanes 12 requires the addition of a catalytic amount of CuCN small middle dot2 LiCl for smooth migration of the alkyl groups. The resultant alpha-silylpentylmagnesium compounds 16 react with electrophiles, such as acyl chlorides or alpha,beta-unsaturated ketones to afford alpha- or gamma-silyl ketones, respectively. Treatment of dibromodisilylmethanes with Me(3)MgLi yields 1-bromo-1,1-disilylethanes 25 that can be converted into 1,1-disilylethenes 29 by dehydrobromination.

Pyridyl Group Assisted Deprotonation of a Methyl Group on Silicon: Complex Induced Proximity Effect and Novel Hydroxymethylation

A novel methodology for the deprotonation of a methyl group on silicon has been developed. This newly developed alpha-lithiation protocol is based on the intramolecular pyridyl group coordination to stabilize the alpha-silyl carbanion together with the inherent silicon alpha effect. It was found that the deprotonation (t-BuLi/Et(2)O/-78 degrees C) occurs with 2-pyridyltrimethylsilane but not with other related silanes such as phenyltrimethylsilane, 3-pyridyltrimethylsilane, and 4-pyridyltrimethylsilane. It seems that this deprotonation proceeded through the agency of the complex-induced proximity effect (CIPE) of a 2-pyridyl group on silicon. (1)H NMR analysis of (2-pyridyldimethylsilyl)methyllithium revealed the intramolecular coordination of a pyridyl group to lithium. (2-Pyridyldimethylsilyl)methyllithium was found to react with chlorosilanes, hydrosilanes, chlorostannanes, bromine, iodine, organic bromides, aldehydes, and ketones in good to excellent yields. The resultant adducts were further oxidized with H(2)O(2)/KF to give the corresponding alcohols in excellent yields. Thus, this two-step transformation provides an efficient method for the nucleophilic hydroxymethylation.

A synthesis of methyl 4,6-dideoxy-3-C-methyl-4-(N-methylacetamido)-alpha-D-altropyr anoside, the 3-epimer of (methyl N-acetylsibirosaminide)

The oxirane ring of 1,6:3,4-dianhydro-beta-D-talopyranose reacted at C-4 with methylamine, and the product, further processed gave a 3-deoxy-C-3-methylene derivative. Iodonium ion-induced cyclisation led to an iodooxazolidinone, and deiodination, followed by hydrolysis and N-acetylation, to the title compound.