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Mark Lautens

Publications and source records attributed to Mark Lautens.

At least 19 recordsLinked to original sources
PubMed2006

Rhodium-catalyzed asymmetric allylic substitution with boronic acid nucleophiles.

An enantio-, regio-, and diastereoselective rhodium(I)-catalyzed desymmetrization of a meso-cyclic allylic dicarbonate with organoboronic acid nucleophiles is described. The rhodium(I) catalyst formed in situ from [Rh(cod)OH]2 and Xyl-P-PHOS allowed the S(N)2' allylic substitution product to be obtained with a range of arylboronic acids in enantiomeric excesses of up to 92% with regioselectivities of up to >20:1.

Boronic Acids↗
PubMed2006

Synthesis of 1,2-dihydropyridines using vinyloxiranes as masked dienolates in imino-aldol reactions.

[reaction: see text] The application of vinyloxiranes, substituted with an electron-withdrawing group, as masked dienolates in vinylogous imino-aldol reactions was achieved. Under the reaction conditions highly substituted 1,2-dihydropyridines were obtained in moderate to good yields. Mechanistic studies indicate that the reaction proceeds via the formation of an (E)-amino-alpha,beta-unsaturated aldehyde, followed by isomerization to the (Z)-isomer, cyclization, and elimination of a water molecule, leading to the formation of the 1,2-dihydropyridine.

Journal Article↗
PubMed2006

Total synthesis of cryptophycin analogues via a scaffold approach.

[reaction: see text] Allylation of in situ generated beta,gamma-unsaturated aldehydes affords rapid access to vinyl halide analogues of fragment A of the cryptophycins. Three scaffolds are prepared in gram quantities by a ring-closing metathesis approach. Derivatization via a variety of cross-coupling protocols is possible, which affords novel analogues of these potent antimitotic agents.

Aldehydes↗
PubMed2006

Synthesis of substituted benzoxacycles via a domino ortho-alkylation/Heck coupling sequence.

The synthesis of a variety of alkylidene benzoxacycles via a domino palladium-catalyzed ortho-alkylation/intramolecular Heck reaction is described. Under the optimized conditions [Pd(OAc)2 (10 mol %), P(2-Furyl)3 (20 mol %), norbornene (4 equiv), Cs2CO3 (2 equiv), CH3CN, 80 degrees C], aryl iodides with oxygen-tethered Heck acceptors are coupled with alkyl bromides (5 equiv) to generate a variety of six- and seven-membered-ring benzoxacyclic products.

Alkylation↗
PubMed2006

Rhodium-catalyzed ring-opening reactions of N-boc-azabenzonorbornadienes with amine nucleophiles.

In the presence of a rhodium catalyst (5 mol %) generated in situ from [Rh(cod)Cl](2) and (S,S')-(R,R')-C(2)-ferriphos (4a), the asymmetric ring-opening reaction of azabenzonorbornadienes (1a-m) with various aliphatic and aromatic amines (2a-l) proceeded with high enantioselectivity (up to >99% ee) to give the corresponding 1,2-diamine derivatives 3 in high yields. In the specific case of pyrrolidine as nucleophile, Et(3)NHCl was necessary as an additive for good reactivity and enantioselectivity. Additionally, a practical protocol was developed for the ring-opening of 1a with volatile amines at elevated temperatures and standard pressure, using R(2)NH(2)I and i-Pr(2)NEt. The experimental results showed that the nature of the chiral ligand has the significant impact on the reactivity of the catalyst and the use of excess amount (2.2 eq to Rh) of the chiral ligand plays an important role to improve the enantioselectivity in the present asymmetric reaction.

Amines↗
PubMed2006

Preparation of annulated nitrogen-containing heterocycles via a one-pot palladium-catalyzed alkylation/direct arylation sequence.

[reaction: see text] A palladium-catalyzed/norbornene-mediated sequential coupling reaction involving an aromatic sp(2) C-H functionalization as the key step is described, in which an alkyl-aryl bond and an aryl-heteroaryl bond are formed in one pot. A variety of highly substituted six- and seven-membered annulated pyrroles and pyrazoles were synthesized in a one-step process in good yields from readily accessible N-bromoalkyl pyrroles or pyrazoles and aryl iodides.

Journal Article↗
PubMed2006

Rhodium-catalyzed tandem vinylcyclopropanation of strained alkenes.

This communication reports an unusual rhodium-catalyzed 1,6-addition of a dienylboronate ester to highly strained alkenes. The resulting vinylcyclopropane-fused tricyclic products were produced in moderate to good yields. Preliminary mechanistic studies are also presented.

Journal Article↗
PubMed2006

Diastereoselective palladium-catalyzed formate reduction of allylic carbonates en route to polypropionate systems.

Diastereoselective palladium-catalyzed formate reduction of allylic carbonates presents unique opportunities for applications in target-oriented organic synthesis provided that selectivity, in particular stereoselectivity, in the course of this metal-catalyzed reaction can be controlled. This article describes our recent developments on new and efficient metal-catalyzed processes exploiting resident stereocenters on the substrates as a means to control stereoselectivity en route to preparing propionate units containing an array of stereochemical patterns. In particular, the effect of the protecting group, the stereochemistry of the aldol adduct, neighboring substituents, and the olefin geometry were examined. Strategic choice of the above parameters provides entry into three of the four possible diastereomeric triads, namely syn-syn, anti-syn, and anti-anti. Preliminary results indicate that construction of the syn-anti triad is possible, albeit in moderate diastereoselectivity.

Journal Article↗
PubMed2006

CuI-Catalyzed tandem intramolecular amidation using gem-dibromovinyl systems.

[reaction: see text] Imidazoindolones are present as the key structural motif in the family of antifungals, fumiquinazolines, and the antagonist asperlicin. The first example of a CuI-catalyzed tandem intramolecular amidation forming substituted imidazoindolones from readily accessible ortho gem-dibromovinylanilines is described.

Antifungal Agents↗