Bernardo Olano

First Highly Regio‐ and Diastereoselective [3+2] Cycloaddition of Chiral Nonracemic Alkenyl Fischer Carbene Complexes with Diazomethane Derivatives: Preparation and Synthetic Applications of Enantiomerically Pure Δ2‐Pyrazolines

Enantiomerically pure orthogonally N,N′-diprotected azaprolines 1 and 2,4-diaminoalcohols 2 are readily accessible by [3+2] cycloaddition of (−)-8-phenylmenthol-derived alkenyl Fischer carbene complexes 3 with diazomethane derivatives.

First highly regio- and diastereoselective synthesis of Δ2-pyrazolines by [3+2] cycloaddition of chiral non-racemic Fischer carbene complexes with nitrilimines

Abstract [3+2] Cycloaddition of Fischer carbene complexes with nitrilimines is described for the first time. The “one-pot” conversion of Fischer carbenes into enantiomerically pure Δ 2 -pyrazolines with high regio- and diastereoselectivity is presented as an expeditious route to these compounds.

First highly regio- and diastereoselective [3+2] cycloaddition of chiral nonracemic Fischer carbene complexes with azomethine ylides: an enantioselective synthesis of (+)-rolipram.

A new procedure for the synthesis of 1,3,4-trisubstituted and 1,4-disubstituted pyrrolidin-2-one derivatives in an enantioselective fashion is reported. The 1,3-dipolar cycloaddition of (+/-)-menthol and (-)-8-phenylmenthol derived Fischer alkoxy alkenyl carbene complexes with in situ generated functionalized azomethine ylides gives the corresponding cycloadducts as chelated tetracarbonyl Fischer carbene complexes. Only one regioisomer is detected in all cases, and the diastereoselectivity of the reaction is very high when (-)-8-phenylmenthol derived carbenes are employed. Oxidation and further transformation of the cycloadducts provide an easy access to pyrrolidin-2-ones. The anti-inflammatory and antidepressant drug (+)-Rolipram is readily prepared in four steps in a 20% overall yield by taking advantage of this newly developed methodology.

α,β-Unsaturated Fischer Carbene Complexes vs. 1,3-Dipoles: Reactions with Nitrones and Nitrilimines

The reaction of tert-butylalkynyl chromium Fischer carbene complex 1 with nitrones 2 affords β-enamino-ketoaldehydes 4 by the light-promoted rearrangement of the corresponding [3+2] cycloadduct carbene complexes 3. On the other hand, [3+2] cycloaddition of chiral nonracemic Fischer alkenyl carbene complexes 19 with nitrilimines 10 yields enantiomerically pure Δ2-pyrazolines with high regio- and diastereoselectivity.

Stereoselective Syntheses of Allylic Amines Through Reduction of 1-Azadiene Intermediates

Abstract The stereoselective synthesis of primary and secondary E-allylic amines by reduction of 1-azadiene intermediates is described. β-Enamino phosphonium salts are suitable starting materials to prepare secondary allylic amines. Two methods are reported for the obtention of primary allylic amines from 4-amino-1-aza-1,3-dienes. Method A leads to the desired compounds by straight reduction with AlH3 or DIBALH; method B is a stepwise procedure that allows for better yields when sterically hindered 4-amino-1-aza-1,3-dienes are employed.

FIRST DIASTEREOSELECTIVE 3+2 CYCLOADDITION OF CHIRAL NON-RACEMIC ALKENYL FISCHER CARBENE COMPLEXES WITH DIAZOMETHANE DERIVATIVES

(-)-8-Phenylmenthol derived pentacarbonylalkenyl(alkoxy)chromium carbene complexes react with diazomethane derivatives to give only one diastereomer of enantiomerically pure 4,5-dihydro-1H-pyrazoles; the one-pot synthesis of the corresponding esters is also described.

New synthesis of 4-amino-1-azadienes by addition of Zn-enolates to nitriles

A synthesis of 4-amino-1-azadienes 1 by addition of Zn-enolates of Schiff bases to nitriles is described. This method improves the yields achieved by the former one using AlCl3.

New synthesis of 4-amino-1-azadienes. First use of Cp2TiMe2 as precursor in insertion reactions of [Cp2Ti=CH2] with nitriles.

Abstract An “ one pot ” procedure for the preparation of symmetric 4-amino-1-azadienes 5 is described. The process constitutes the first performance of insertion reactions of the complex [Cp 2 Ti=CH 2 ] with nitriles starting from Cp 2 TiMe 2 .

Diastereo- and enantio-selective synthesis of dihydro- and tetrahydro-pyrimidines. A new strategy for the asymmetric synthesis of β-amino ketones and γ-amino alcohols

Chiral 1,2-dihydro-(3) and 1,2,3,6-tetrahydro-pyrimidines (4) have been synthesized by reaction of 3-aminoalk-2-enimines (1) with chiral aldehydes, the structure of (4) being confirmed by an X-ray crystal structure determination of a reduction product; a new strategy for the asymmetric synthesis of β-amino ketones (2) and γ-amino alcohols (6) with two or three chiral centres is described.

A simple stereoselective synthesis of primary allylic amines from 4-amino-1-azadienes

A new and efficient synthesis of primary allylic amines (2) from 4-amino-1-azadines (1)via 1-azadienes (5) by reduction processes is described; the process is very simple, highly stereoselective, and takes place with very high chemical yields.