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Shengming Ma

Publications and source records attributed to Shengming Ma.

At least 19 recordsLinked to original sources
PubMed2007

Studies on Pd(0)-catalyzed cyclization of N-3,4-alkadienyl toluenesulfonamides with organic halides: selective synthesis of 2,3-dihydropyrroles, 1,2,3,6-tetrahydropyrridines, and azetidines.

The palladium-catalyzed coupling-cyclization of beta-amino allenes with organic halides ranging from aryl halide to 1-alkenyl halide was studied. 2,3-Dihydro-1H-pyrroles were obtained by reaction of 3-substituted-5-unsubstituted-3,4-allenyl amides under conditions A, while the reaction of 5-substituted-3,4-allenyl amides afforded 1,2,5,6-tetrahydropyridines and/or azetidines with high de under conditions B or C. The skeleton and relative configuration of the six-membered products were established by the X-ray diffraction studies of 10 ka. Allenyl amide 4 q reacted with 1,4-diiodobenzene 6 r to afford double cyclization product 15. The structure of its major stereoisomer was also determined by the X-ray diffraction study.

Journal Article↗
PubMed2006

Palladium-catalyzed functionalization of indoles with 2-acetoxymethyl-substituted electron-deficient alkenes.

New functionalizations of indoles via palladium-catalyzed reaction of indoles and 2-acetoxymethyl-substituted electron-deficient alkenes are reported. It was found that for N-protected indoles the reaction proceeded smoothly in the presence of 5 mol % of Pd(acac)2 and 10 mol % of PPh3 at 80 degrees C in HOAc, while for N-unprotected indoles, the reaction was carried out by using 5 mol % of Pd(dba)2 or 2.5 mol % of Pd2(dba)3.CHCl3 with 10 mol % of 2,2'-bipyridine as the catalyst in toluene. This strategy allows the selective installation of electron-deficient olefin functionality at the 3-position of indoles, which might be difficult to obtain by other methods and can be further elaborated.

Alkenes↗
PubMed2006

Electrophilic interaction of 2,3-allenoates with PhSeCl. An unexpected highly stereoselective synthesis of 3-phenylseleno-4-oxo-2(E)-alkenoates.

We have previously reported an efficient synthesis of beta-phenylselenium-substituted butenolides via electrophilic cyclization of 2,3-allenoates with PhSeCl in aqueous MeCN. However, when 2,3-allenoates were treated with PhSeCl in MeCN, 3-phenylseleno-4-oxo-2(E)-alkenoates were formed unexpectedly. The addition of Li2CO3 improved the yield and the selectivity of the reaction. A possible mechanism involving a decomposition of selenate esters was proposed.

Journal Article↗
PubMed2006

Palladium(0)-catalyzed highly regio- and stereoselective addition of organoboronic acids with 1,2-allenylphosphonates forming tri- or tetrasubstituted 1(E)-alkenylphosphonates.

A highly regio- and stereoselective palladium(0)-catalyzed addition of organoboronic acids with 1,2-allenylphosphonates in the presence of HOAc forming tri- or tetrasubstituted 1(E)-alkenylphosphonates is reported in this paper. The stereoselectivity is much higher than the reported cases. The effects of different R(1), R(2), and R(3) were studied. A mechanism of this reaction is proposed on the basis of our previous study.

Journal Article↗
PubMed2006

A water-compatible, highly active and reusable PEG-coated mesoporous silica-supported palladium complex and its application in Suzuki coupling reactions.

A highly active heterogeneous palladium catalyst was prepared from coated mesoporous materials which contain a layer of readily available PEG with a labile coordinating ability for palladium. The aqueous suspension of the catalyst may be reused several times by simple extraction of the aqueous reaction mixture with ether to remove the product.

Catalysis↗
PubMed2006

Sequential rearrangement of 1,2,4Z,7-tetraenes involving [1,5]-hydrogen migration and electrocyclization: an efficient synthesis of eight-membered cyclic compounds.

An efficient protocol for the synthesis of eight-membered bicyclic compounds from the cycloisomerization of 1,2,4Z,7-tetraenes has been established. The possible intermediate for this transformation was trapped by its Diels-Alder reaction with N-ethyl maleimide. Thus the reaction may proceed via the sequential processes involving [1,5]-hydrogen migration and electrocyclization.

Journal Article↗
PubMed2006

Studies on the Cu(I)-catalyzed regioselective anti-carbometallation of secondary terminal propargylic alcohols.

A highly regioselective Cu(I)-catalyzed anti-carbometallation of secondary terminal propargylic alcohols with 1 degrees alkyl or aryl Grignard reagents affording 2-substituted allylic alcohols was developed. By using this method, optically active allylic alcohols can be prepared from the optically active propargylic alcohols without obvious loss of the enantiopurity. The cyclic organometallic intermediate formed may undergo an iodination or a Pd(0)-catalyzed coupling reaction to afford stereo-defined allylic alcohols.

Journal Article↗
PubMed2005

1,4-migration of rhodium and palladium in catalytic organometallic reactions.

Mechanisms based on the 1,4-migration of metal centers have been proposed to explain some interesting transition-metal-catalyzed organic transformations. Despite the lack of solid evidence for the real nature of this process, the 1,4-metal migration reaction is proposed to proceed by the reductive elimination of trivalent intermediates for the Rh-involved reactions and of tetravalent intermediates for the Pd-catalyzed processes. These high-valent organometallic species would be formed by the oxidative addition to C-H and C-X bonds. This minireview summarizes the results in this area.

Journal Article↗
PubMed2005

From allene to allene: a palladium-catalyzed approach to beta-allenyl butenolides and their application to the synthesis of polysubstituted benzene derivatives.

An allene to allene protocol for the synthesis of beta-allenyl butenolides in moderate to high yields from 2,3-allenoic acids and propargylic carbonates catalyzed by Pd(OAc)2-TFP has been developed; the products were applied successfully to the Diels-Alder reaction with electron-deficient alkynes to afford polysubstituted benzene derivatives with an excellent regioselectivity.

Journal Article↗
PubMed2005

Sc(OTf)3-catalyzed indolylation of 1,2-allenic ketones: controlled highly selective synthesis of beta-indolyl-alpha,beta-unsaturetated (E)-enones and beta,beta-bisindolyl ketones.

[reaction: see text] A novel highly stereoselctive synthesis of beta-indolyl-alpha,beta-unsaturated (E)-enones by the hydroindolylation of the beta,gamma-C=C bond of 1,2-allenic ketones in the presence of 5 mol % Sc(OTf)(3) was developed. beta,beta-Bisindolyl ketones were prepared by using 2.5 equiv of indoles. A stepwise protocol for introducing different indoles was also established.

Catalysis↗
PubMed2005

An efficient stereoselective synthesis of 4,5-trans-1,5-cis-3-oxabicyclo[3.1.0]hexan-2-ones via the iodolactonization of alkylidenecyclopropyl esters.

[reaction: see text] A highly stereoselective iodolactonization of alkylidenecyclopropyl esters with iodine or N-iodosuccinimide (NIS) in aqueous CH3CN to afford 4,5-trans-1,5-cis-3-oxabicyclo-[3.1.0]hexane-2-ones is described. The reaction is very general, accommodating a wide range of substituents. A plausible mechanism that explains the essential role of water in this reaction is proposed.

Journal Article↗