José M. Saá

Enantioselective cyanoformylation of aldehydes mediated by BINOLAM–AlCl as a monometallic bifunctional catalyst

Abstract BINOLAM–AlCls, binaphthoxide aluminium chloride species generated in situ from either ( R )- or ( S )-3,3′-bis(diethylaminomethyl)-2,2′-dihydroxy-1,1′-binaphthalene (BINOLAM) behave as Lewis acid–Lewis base (LA-LB) catalysts in the enantioselective addition of methyl cyanoformate to aldehydes at room temperature, thereby leading to the asymmetric synthesis of ( S )- or ( R )- O -methoxycarbonyl cyanohydrins, respectively.

Enantioselective, organocatalytic Morita-Baylis-Hillman and Aza-Morita-Baylis-Hillman reactions: stereochemical issues.

Conscious of the importance that stereochemical issues may have on the design of efficient organocatalyts for both Morita-Baylis-Hillman and aza-Morita-Baylis-Hillman reaction we have analyzed them in this minireview. The so-called standard reactions involve “naked” enolates which therefore should lead to the syn adducts as the major products, irrespective of the E, Z stereochemistry of the enolate. Accordingly, provided the second step is rate determining step, the design of successful bifunctional or polyfunctional catalysts has to consider the geometrical requirements imposed by the transition structures of the second step of these reactions. On the other hand, MBH and aza-MBH reactions co-catalyzed by (S)-proline and a secondary or tertiary amine (co-catalyst) involve the aldol-type condensation of either a 3-amino-substituted enamine, dienamine, or both, depending on the cases. A Zimmerman-Traxler mechanism defines the stereochemical issues regarding these co-catalyzed condensations which parallel those of the well established (S)-proline catalyzed aldol-like reactions.

Palladium catalyzed cross-coupling of phenol triflates with organostannanes. A versatile approach for the synthesis of substituted resorcinol dimethyl ethers.

Abstract -2,6 Dimethoxy-substituted phenol triflates undergo efficient Pd(O) catalyzed cross coupling with organostannanes, thus providing an easy access to substituted resorcinol dimethyl ethers, a common building block of many aromatic polyketides.

Oxocompostelline and oxocularine, structure and synthesis

Abstract Structures ( 1 ) and ( 2 ) were deduced for these two new oxocularine alkaloids from spectral data and synthesis. The latter was achieved by a novel approach based on intramolecular cyclization between a phenoxide and an intermediate benzyne.

New benzyne approach to the synthesis of dehydroaporphines, 4,5-dioxoaporphines and aristolactams

Abstract A new strategy for the synthesis of some aporphinoid alkaloids is described. It is based on the intermolecular Diels-Alder cyclization between benzyne and an appropriate methylene isoquinoline derivative.

Enantioselective synthesis of (S)-α-methylphenylalanine using (S)-BINOLAMs as new phase-transfer catalysts

Abstract A series of (S)-bis(aminomethyl)binaphthols [(S)-BINOLAMs] 4 have been prepared and used as catalysts in the enantioselective C-alkylation reaction of the aldimine Schiff bases of alanine esters 5 under solid–liquid phase-transfer catalysis (PTC) conditions employing NaOH as base in toluene at room temperature. (S)-3,3′-Bis[(diethylamino)methyl]-2,2′-dihydroxy-1,1′-binaphthalene 4a gave the best e.e.s. (S)-α-Methylphenylalanine 7 was isolated, after hydrolysis of the iminoester, in 85% yield with an e.e. of 68%.

Ribasine, a new class of papaveraceae alkaloids

Abstract The structure (including absolute stereochemistry), of ribasine, a new class of papaveraceae alkaloids with an indanobenzazepine skeleton, has been established. It was isolated from Sarcocapnos crassifolia and Corydalis claviculata .

New phenolic isocularine and benzylisoquinoline alkaloids and their biogenetic relationship

Abstract The first three phenolic isocularines and the first diphenolic 7,8,3′,4′-tetraoxygenated tetrahydrobenzylisoquinoline were isolated from Sarcocapnos crassifolia. A pathway for the biogenesis of cularine is considered.

The reaction of 1-alkyldihydroisoquinolines with benzyne. An unexpected entry to dibenzindolizines

Abstract The reaction of 1-ethylidene-2-formyl-1,2,3,4-tetrahydroisoquinolines 4a and 4b , or 1-ethyl-3,4-dihydroisoquinolines 3a and 3b , with benzyne led, by a formal 3+2 cycloaddition, to dibenzindolizines 5a and 5b , respectively. Compound 5b was also synthesized by photocyclization of enamine 6 .

The intermolecular benzyne cycloaddition approach to dehydronoraporprines and oxoaporphines. Total synthesis of PO-3

Abstract The synthesis of dehydronoraporphines and oxoaporphines has been achieved by means of the convergent and highly regioselective intermolecular benzyne cycloaddition approach. The first total synthesis of the quaternary oxoaporphine PO-3 is described.