Javier Vicario

Abstract: A diastereoselective inverse electron demand aza-Diels-Alder reaction of N-aryl-1-azadienes derived from α-amino acids is accomplished using enamine dienophiles. Activation with ytterbium triflate of these azadienes affords dimeric structures through aza-Diels-Alder reaction, where the alkene double bond of 1-azadienes also adopts the role of dienophile. An asym. synthesis of functionalized 1,4,5,6-tetrahydropyridine compds. derived from α-amino acids using an optically active enamine is reported. [on SciFinder(R)]

Abstract: The synthesis of α-iminophosphonates derived from ketones was achieved by aza-Wittig reaction of P-trimethylphosphazenes with acylphosphonates. These unstable compds. can be used for the synthesis of chiral α-aminophosphonate derivs. through addn. of nucleophiles to the C-N iminic double bond. Moreover, if α,β-unsatd. imines are used, regioselective Michael addn. to the conjugated bond yields α-dehydroamino-phosphonic acid derivs. functionalized at the γ-position. [on SciFinder(R)]

Abstract: A review. The purpose of this article is to illustrate synthetic aspects of functionalized phosphorus derivs. contg. an oximo moiety at the beta-position. First section will be focused on the synthesis of phosphine oxides, phosphonates or phosphonium salts contg. an oxime group. The synthesis of these derivs. comprises the carbon-phosphorus single bond construction by reaction of haloximes with phosphorus derivs., nucleophilic addn. of phosphorus reagents to carbonyl compds., or nucleophilic addn. of phosphorus reagents to nitro olefins. This section will also conc. on the most practical routes for the synthesis of the target compds., through carbon-nitrogen double bond formation, which are as follows: condensation processes of carbonyl compds. and hydroxylamine derivs. or addn. of hydroxylamines to allenes or alkynes. The preparative use of beta-oximo phosphorus derivs. as synthetic intermediates will be discussed in a second section, comprising olefination reaction, oxidn. of oximes to nitrile oxides by reaction at the C-N double bond of the oxime moiety, oxidn. of these substrates to nitrosoalkenes, redn. to the corresponding hydroxylamines and some reactions at the hydroxyl group of the hydroxyimino moiety. [on SciFinder(R)]

Abstract: This review summarizes several reports concerning the synthesis and synthetic applications of hydroxylamines derived from phosphines, phosphine oxides and phosphonates, and P-substituted hydroxamic acid derivs. The first section outlines the synthesis and reactivity of phosphorus O-substituted and N-substituted hydroxylamines as well as several transformations of P-substituted hydroxylamines including rearrangement, hydrolysis, redn., and oxidn. reactions. The second part covers the synthesis and reactivity of phosphorus O-, N-, and C-substituted hydroxamic acid derivs. [on SciFinder(R)]

Abstract: Efficient synthesis of α-aminophosphonic acid derivs. is achieved, the key step being a diastereoselective hydrophosphonylation of N-diphenylphosphinyl imines using a readily available chiral cyclic (R,R)-TADDOL-phosphite derived from inexpensive natural tartaric acid. [on SciFinder(R)]

Abstract: A review. The structural and synthetic aspects related to α-oxyiminophosphorus derivs. are reviewed. This includes their prepn. through reactions involving C-N double bond or P-C single bond formation as well as the O-functionalization or transformations at the phosphorus atom of other phosphorus substituted oximes. Moreover the synthetic features of α-oxyiminophosphorus derivs. include the redn. of the oximo group with selective prepn. of biol. active α-amino-phosphonate and -phosphinate derivs., as well as the oxidative transformations on the oxime group, rearrangement vs. fragmentation reactions, radical reactions and formation of metal complexes. [on SciFinder(R)]

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Abstract: Herein, we report a novel approach to achieving optimum spatial and energetic arrangement of donor and acceptor units immobilized on glass and ITO surfaces, in which the optimum ratio of energy-donor and -acceptor units is detd. by the monolayer itself once formed. We use the irreversible photochem. of the bistricyclic arom. enylidene (BAE)-based fluorophores to generate the acceptor unit in situ from the surface-immobilized donor units themselves. [on SciFinder(R)]

Abstract: Aza-Michael addn. of amines R1R2NH to conjugated α-iminoallylphosphonate ArN:CXCH:CHMe [1, Ar = 4-NO2C6H4, X = P(O)(OEt)2] gave enamino-phosphonates (E)-ArNHCX:CHCHMeNR1R2 [3a-e; R1 = H, R2 = H, 4-MeC6H4, 4-NO2C6H4, Me,; R1-R2 = (CH2)4; R1R2NH = (S)-methoxymethylpyrrolidine, (S)-pseudoephedrine]. Aliph. amines H2NCH2R3 gave (Z)-isomers (Z)-ArNHCX:CHCHMeNHR3 (5a-c, R3 = Ph, CH:CH2, C≡CH) or (Z-E) mixts. (7a,b, R3 = Et, iPr), which undergo Z-E-isomerization, catalyzed by Et3N, giving the corresponding pure (E)-isomers (3h-l). Reaction of triphosgene with (Z)-ArNHCX:CHCHMeNHR3 (R3 = Ph, CH:CH2) gave phosphono-substituted pyrimidines 1-Ar-3-CH2R3-4-Me-6-X-2-pyrimidinones (11a,b, same Ar, X, R3). [on SciFinder(R)]

Abstract: In this contribution, zinc-5,10,15,20-meso-tetradodecylporphyrins (Zn-TDPs) self-assemble into stable organized arrays on the surface of graphite, thus positioning their metal center at regular distances from each other, creating a mol. pattern, while retaining the possibility to coordinate addnl. ligands. Also Zn-TDPs coordinated to 3-nitropyridine display a higher tendency to be adsorbed at the surface of highly oriented pyrolytic graphite (HOPG) than noncoordinated ones. To study the two-dimensional (2D) self-assembly of coordinated Zn-TDPs, solns. with different relative concns. of 3-nitropyridine and Zn-TDP were prepd. and deposited on the surface of HOPG. STM measurements at the liq.-solid interface reveal that the ratio of coordinated Zn-TDPs over noncoordinated Zn-TDPs is higher at the n-tetradecane/HOPG interface than in n-tetradecane soln. This enhanced binding of the axial ligand at the liq./solid interface is likely related to the fact that physisorbed Zn-TDPs are better binding sites for nitropyridines. [on SciFinder(R)]

Abstract: We report the synthesis of unidirectional light-driven rotary mol. motors based on chiral over-crowded alkenes and their immobilization on the surface of gold nanoparticles through two anchors. Using a combination of 1H and 13C NMR, UV/Vis and CD spectroscopy, we show that these motors preserve their photochem. and thermal behavior after they have been attached to gold nanoparticles. Furthermore, we describe the synthesis of 2H- and 13C-labeled derivs. that were used to verify the unidirectionality of the rotary cycle of these motors both in soln. and while grafted to gold nanoparticles. Taken together, these data support the conclusion that these motors maintain their unidirectional rotary cycle when grafted to the surface of small (ca. 2 nm) gold nanoparticles. Thus, continuous irradn. of the system under appropriate conditions leads to unidirectional rotation of the upper half of the mols. relative to the entire nanoparticle. [on SciFinder(R)]

Abstract: α,β-Unsatd. sulfinyl imines derived from α-amino acids undergo aza-Diels-Alder reaction with electron-rich dienophiles such as enol ethers and enamines. Subsequent elimination of sulfinyl and amine or alkoxy moiety on the resulting cycloadducts affords pyridines derived from α-amino acids. [on SciFinder(R)]

Abstract: Copper-catalyzed asym. 1,4-addn. of diethylzinc to β,γ-unsatd. α-imino esters I (R = Me, R1 = NO2; R = MeO, R1 = NO2; R = R1 = Me; R = NO2, R1 = Me) using a copper-phosphoramidite complex affords the resp. enantiomerically enriched γ-functionalized dehydro α-amino esters II. [on SciFinder(R)]

Abstract: An efficient synthesis of α,β-unsatd. imines derived from α-aminophosphonates is achieved through aza-Wittig reaction of P-trimethyl phosphazenes with β,γ-unsatd. α-ketophosphonates. Selective 1,2-redn. of such 1-azadienes affords β,γ-unsatd. α-aminophosphonates, phosphorylated analogs of vinylglycines, which are hydrogenated to yield satd. α-aminophosphonate derivs. [on SciFinder(R)]

Abstract: The introduction of bulky substituents at the stereogenic center of light-driven second-generation mol. motors results in an acceleration of the speed of rotation. This is due to a more strained structure with elongated C:C bonds and a higher energy level of the ground state relative to the transition state for the rate-limiting thermal isomerization step. Understanding the profound influence that variation of the substituent at the stereogenic center holds over the rotational speed of the light-driven mol. motor has enabled the development of the fastest mol. motor reported thus far. [on SciFinder(R)]

Abstract: Aminopyrrolones I are prepd. either from primary amines RNH2 [R = 4-MeC6H4, 4-MeOC6H4, 4-ClC6H4, (S)-PhCH(Me)] and (E)-β,γ-unsatd.-α-ketoesters (E)-R1CH:CHC(:O)CO2Et [R1 = Me, EtO2C, 2-furyl, 4-O2NC6H4, (E)-PhCH:CH] or by a one-pot cyclocondensation of amines RNH2 [R = 4-MeC6H4, 4-MeOC6H4, 4-ClC6H4, (R)-PhCH(Me)], aldehydes R1CHO [R1 = Me, EtO2C, 2-furyl, 4-O2NC6H4, (E)-PhCH:CH], and Et pyruvate in the presence of titanium tetraethoxide and sulfuric acid. (E)-β,γ-unsatd.-α-oxoesters (E)-R1CH:CHC(:O)CO2Et [R1 = Me, EtO2C, 2-furyl, 4-O2NC6H4, (E)-PhCH:CH] are prepd. either by Wittig-Horner or Wittig olefinations of Ph2P(:O)CH2CO2Et or Ph3P:CHCO2Et with R1CHO [R1 = Me, EtO2C, 2-furyl, 4-O2NC6H4] or by aldol condensation of Et pyruvate with R1CHO [R1 = 2-furyl, 4-O2NC6H4, (E)-PhCH:CH]. Cyclocondensation of (R)-α-methylbenzylamine and (E)-4-O2NC6H4CH:CHC(:O)CO2Et gives a 1:1 mixt. of diastereomeric pyrrolones. Attempted cyclocondensation of (E,E)-PhCH:CHCH:CHC(:O)CO2Et with p-toluidine yields a dihydropyridine as the sole product. [on SciFinder(R)]

Abstract: A mol. motor in a liq.-crystal film uses light to turn items thousands of times larger than itself. [on SciFinder(R)]

Abstract: The structure of mol. monolayers formed at the interface between atomically flat surfaces and a soln. of free-base meso-tetradodecylporphyrins (H2Ps) was examd. by scanning tunneling microscopy (STM) at the liq./solid interface. On the surface of graphite (HOPG), H2Ps form a well-ordered monolayer characterized by an oblique unit cell. On Au(111), H2Ps form a self-organized monolayer comprised of two distinct domain types. In both types of domains, the d. of the porphyrin cores is increased in comparison to the arrangement obsd. on HOPG. Also, high-resoln. STM images reveal that, in contrast to what is obsd. on HOPG, physisorption on Au(111) induces a distortion of the porphyrin macrocycle out of planarity. By using XPS, we demonstrate that this is likely to be due to the coordination of the lone pairs of the iminic (-C:N-) nitrogen atoms of the porphyrin macrocycle to Au(111). [on SciFinder(R)]

Abstract: Selective conjugate reaction (1,4-addn.) of PPh3-derived N-arylphosphazenes to α,β-unsatd. carbonyl compds. yielded 2-quinolinecarboxylates. However, when more reactive, PMe3-derived phosphazene species were used, selective reaction with the carbonyl carbon (1,2-addn.) occurred and N-aryl-1-azadienes were obtained. Thermal 6π-aza-electrocyclization of these 1-azadienes afforded 4-quinolinecarboxylates. [on SciFinder(R)]

Abstract: An efficient synthesis of 1-azadienes derived from α-aminoesters I (R1 = 4-MeC6H4, 4-NO2C2H4, 4-MeOC6H4; R2 = 4-NO2C6H4, 4-MeC6H4, Me, 2-furyl, CO2Et) is achieved through an aza-Wittig reaction of phosphazenes with β,γ-unsatd. α-ketoesters. Regioselective 1,2-redn. of these functionalized 1-azadienes affords vinylglycine derivs. II, while conjugative 1,4-redn. gives α-dehydroamino acid compds. III. Redn. of both the carbon-carbon and the imine-carbon-nitrogen double bonds leads to the formation of α-amino acid derivs. [on SciFinder(R)]

Abstract: In this paper an unprecedented rotational reorganization of cholesteric liq. cryst. films is described. This rotational reorganization results from the conversion of a chiral mol. motor dopant to an isomer with a different helical twisting power, leading to a change in the cholesteric pitch. The direction of this reorganization is correlated to the sign of the change in helical twisting power of the dopant. The rotational reorganization of the liq. cryst. film was used to rotate microscopic objects 4 orders of magnitude larger than the bistable dopants in the film, which shows that mol. motors and switches can perform work. The surface of the doped cholesteric liq. cryst. films was found to possess a regular surface relief, whose periodicity coincides with typical cholesteric polygonal line textures. These surface features originate from the cholesteric superstructure in the liq. cryst. film, which in turn is the result of the presence of the chiral dopant. As such, the presence of the dopant is expressed in these distinct surface structures. A possible mechanism at the origin of the rotational reorganization of liq. cryst. films and the cholesteric surface relief is discussed. [on SciFinder(R)]

Abstract: A highly enantioselective synthesis of α-dehydroamino acids I (R1 = p-Me-Ph, p-MeO-Ph, R2 = p-NO2-Ph, R3 = Et; R1 = p-MeO-Ph, p-NO2-Ph, R2 = p-Me-Ph, R3 = Me) with a stereogenic center in the γ position through copper-catalyzed asym. conjugate addn. of diethylzinc to α,β-unsatd. imines II (R1 = p-Me-Ph, p-MeO-Ph, R2 = p-NO2-Ph, R3 = Et; R1 = p-MeO-Ph, p-NO2-Ph, R2 = p-Me-Ph, R3 = Me) using a TADDOL-derived phosphoramidite complex III is reported. [on SciFinder(R)]

Abstract: Oxidn. of hydrazone I with hypervalent iodine reagent PhI(OCOCF3)2 gave the corresponding diazo compd., which readily underwent 1,3-dipolar cycloaddn. reaction with thioketones II (X = O, S, Me2C, CH:CH; R = H, O2N, MeO) accompanied by nitrogen extrusion to afford thiiranes III. Subsequent desulfurization of III with PPh3 in p-xylene gave overcrowded alkenes IV in 81-90% yields. [on SciFinder(R)]

Abstract: A mol. approach to the powering of multi-component nano-devices capable of autonomous translational and rotational motion through the conversion of chem. to kinetic energy is reported. [on SciFinder(R)]

Abstract: Substitution of a 6-membered by a 5-membered ring upper half in the light driven second generation mol. motors resulted in a dramatic increase of the speed of rotation. [on SciFinder(R)]

Abstract: Mols. capable of mimicking the function of a wide range of mech. devices have been fabricated, with motors that can induce mech. movement attracting particular attention. Such mol. motors convert light or chem. energy into directional rotary or linear motion, and are usually prepd. and operated in soln. But if they are to be used as nanomachines that can do useful work, it seems essential to construct systems that can function on a surface, like a recently reported linear artificial muscle. Surface-mounted rotors have been realized and limited directionality in their motion predicted. Here we demonstrate that a light-driven mol. motor capable of repetitive unidirectional rotation can be mounted on the surface of gold nanoparticles. The motor design uses a chiral helical alkene with an upper half that serves as a propeller and is connected through a carbon-carbon double bond (the rotation axis) to a lower half that serves as a stator. The stator carries two thiol-functionalized 'legs', which then bind the entire motor mol. to a gold surface. NMR spectroscopy reveals that two photo-induced cis-trans isomerizations of the central double bond, each followed by a thermal helix inversion to prevent reverse rotation, induce a full and unidirectional 360° rotation of the propeller with respect to the surface-mounted lower half of the system. [on SciFinder(R)]

Abstract: Quinolinealkylphosphine oxides are obtained by thermal treatment of N-arylimines derived from phosphine oxides with N,N-dimethylformamide di-Et acetal (DMF-DEA). In a similar manner, quinolinealkylphosphonates are obtained by reaction of DMF-DEA with N-arylimines derived from phosphonates or from their precursors, arylamines and carbonyl derivs. [on SciFinder(R)]

Abstract: Quinolinylphosphine oxides are obtained by heterocyclization of N-arylimines derived from phosphine oxides with DMF di-Et acetal (DMF-DEA). Arylimines ArN:CMeCH2POPh2 (1c-e) were prepd. by ArNH2 condensation with CH2:C:CHPOPh2 (Ar = 4-ClC6H4, 3-CF3C6H4, 3,4-Me2C6H3). The quinolines 2-R1-3-POPh2-6-R2-7-R3-C9H3N (5a-g) were prepd. by heterocyclization of arylimines ArN:CR1CH2POPh2 1a-g with DMF-DEA (R1, R2, R3: a Me, Me, H; b Me, OMe, H; c Me, Cl, H; d Me, H, CF3; e Me, Me, Me; f Et, Me, H; g H, OMe, H). An intermediate N-aryl-1-azadiene 4-MeC6H4N:CMeC(POPh2):CHNMe2 (4a) was isolated and cyclization thereof leads to phosphinylated quinoline 5a. In a similar manner, quinolinylphosphonates 2-R1-3-PO(OEt)2-6-R2-7-R3-C9H3N (8a-d) were prepd. by one-pot reaction of oxophosphonates R1COCH2PO(OEt)2, arylamines 4-R2-3-R3C6H3NH2 and DMF-DEA (R1, R2, R3: 8a H, H, H; 8b Me, Me, H; 8c Me, OMe, OMe; 8d Me, H, H). [on SciFinder(R)]

Abstract: α-Substituted (2-iminoalkyl)phosphane oxides, I (R1 = p-CH3-Ph, (S)-Ph-CH-Me, Ph2CH, etc. and R2 = CH2CO2Et, Et, allyl, etc.) were obtained from the azaenolates of imines or enamines and alkyl halides. The functionalized imines or enamines thus obtained were used for the synthesis of δ-amino esters, δ-amino phosphonates and heterocycles such as 3,4-dihydropyridin-2-ones, 2-pyridones and pyrroles contg. a phosphinyl substituent. [on SciFinder(R)]

Abstract: Functionalized hydrazones derived from phosphine oxides or phosphonates were obtained from azaenolates of hydrazones and alkyl halides. The regioselectivity of alkylation of α-phosphorylated hydrazones can be controlled by P moiety. α-Alkylated compds. were used for the synthesis of heterocycles such as 1-aminopyrrol-2-ones, 1-amino-3,4-dihydropyridin-2-ones and 1-aminopyrroles contg. phosphinyl or phosphoryl substituents. [on SciFinder(R)]