Tadao Uyehara

Synthesis of chiral [5]helicenes using aromatic oxy-Cope rearrangement as a key step

Abstract Both enantiomers of ( P )-(+)-2- and ( M )-(−)-2-acetoxy-11,14-dimethyl[5]helicenes 8 were synthesized by asymmetric aromatic oxy-Cope rearrangement of the corresponding chiral bridged bicyclic compounds, which were obtained by enzymatic resolution. The absolute configurations of 8 were assigned by their circular dichroism spectra.

Synthesis of 2-acetoxy[5]helicene by sequential double aromatic oxy-Cope rearrangement

Abstract Synthesis of 2-acetoxy[5]helicene has been achieved by sequential double aromatic oxy-Cope rearrangement strategy. Combination of 1-methoxybicyclo[2.2.2]oct-5-en-2-one and p -bromophenylmagnesium bromide gave 3-bromophenanthrene through several steps including an aromatic oxy-Cope rearrangement as a key step. The second oxy-Cope rearrangement and the following transformation gave 2-acetoxy[5]helicene by similar procedure.

Synthesis of tetrahydrofurans by regio- and stereoselective cyclization of epoxyalcohols using magnesium halide

Abstract A novel synthetic method for several tetrahydrofuran derivatives by intramolecular cyclization of epoxyalcohols is described. The presence of a catalytic amount of magnesium halide altered the regio- and stereoselectivity of the cyclization reaction.

Highly stereodivergent generation of the Z- and E-enolates of a β-amino ester via conjugate addition to methyl crotonate by using lithium N-benzyltrimethylsilylamide as a nitrogen nucleophile, and application to stereoselective aldol reactions

Methods for highly stereoselective generation of both Z- and E-enolates of a β-amino ester have been developed on the basis of a conjugate addition of lithium N-benzyltrimethylsilylamide to methyl crotonate and applied to stereoselective synthesis of anti,syn- and syn,anti-β-amino-β′-hydroxy esters by treatment with aldehyde.

Cyclisation of α,β,γ,ψ-unsaturated dioic acid esters via tandem conjugate additions by using lithium N-benzyltrimethylsilylamide (LSA) as a nitrogen nucleophile and its application to a total synthesis of (±)-dihydronepetalactone and (±)-isodihydronepetalactone

A stereoselective total synthesis of (±)-dihydronepetalactone and (±)-isodihydronepetalactone has been accomplished by utilising a novel cyclisation procedure; a reaction of octadiene-2,6-dioic acid esters with lithium N-benzyltrimethylsilylamide (LSA) induces 5-exo-Trig ring-closure via tandem conjugate additions.

Stereoselective α-alkylation of α,β-unsaturated esters utilizing conjugate addition of nitrogen nucleophiles (R2NLi)

Treatment of α,β-unsaturated esters (1) with lithium amides [LiNPri2 and LiN(CH2Ph)SiMe3] followed by alkylation and elimination of the amino groups produced trisubstituted enoates (2) with high stereoselectivity.

Formal substitution at both bridgeheads of a bicyclo[2.2.2]oct-5-en-2-one and its application to a synthesis of (±)-modhephene

Abstract Synthesis of a propellane sesquiterpene (±)-modhephene ( 23 ) was achieved on the basic of a novel procedure to introduce the desired alkyl groups at both bridgeheads of a bicyclo[2.2.2]oct-5-en-2-one.

The first total synthesis of (±)-2-thiocyanatoneopupukeanane based on a pinacol-type rearrangement

The racemic mixture of 2-thiocyanatoneopupukeanane, a marine sesquiterpene-thiocyanate with a tricylo[4.3.1.03,7]decane skeleton, was prepared through a pinacol-type rearrangement of a bicyclo[2.2.2]oct-5-en-2-ol giving a bicyclo[3.2.1]oct-6-en-2-one derivative and an aldol reaction leading to the neopupukeanane framework.

Novel aromatic oxy-Cope rearrangement. Participation of a benzene ring and intramolecular potassium-ion detachment by methoxy groups

Abstract The aromatic oxy-Cope rearrangement including a benzene ring took place when 1-methoxy-2-aryl-bicyclo[2.2.2]oct-5-en-2- exo -ols and 2-(2-methoxyphenyl)-bicyclo[2.2.2]oct-5-en- exo -2-ols were treated with KH in THF.

Total synthesis of (±)-nakafuran-8, a marine metabolite with antifeedant properties, based on formal bridgehead substitution of a bicyclo[2.2.2]oct-5-en-2-one system

The first total synthesis of (±)-nakafuran-8, a furanosesquiterpene containing a bicyclo[4.2.2]decane skeleton, has been accomplished starting from 1-methoxy-4,5,8-endo-trimethylbicyclo[2.2.2]oct-5-en-2-one by a rearrangement strategy including the formal bridgehead substitution of this methoxy group by hydrogen on the basis of a pinacol-type rearrangement and the double ring-enlargement of this product to give 6,7,10-exo-trimethyl-bicyclo[4.2.2]dec-7-en-2-one via the bicyclo[3.2.2]non-6-en-2-one.