Benzylic modifications of meso-alkyl-substituted porphyrins via oxidation with DDQ

The reactions at the benzylic positions of meso-alkyl-substituted porphyrins have been achieved via the reaction with DDQ in the presence of alcohol or water for the first time, and ethenyl porphyrins from methoxylated porphyrins and an acetoxy porphyrin from the hydroxyl porphyrin were prepared.     

Ultrasonicwave-assisted tandem-reaction for synthesis of symmetrical vicinal diamines

A practical synthesis of symmetrical vicinal diamines with broad chemistry scope is described.The key step is the ultrasonicwave promoted tandem-reaction,two-step reaction sequence combining Mannich double condensations with benzo- triazole,glyoxal and primary or secondary amines and reduction of the bis(benzotriazole)-adducts with sodium borohydride proceeded smoothly in tetrahydrofuran in high yield at room temperature.     

Facile solid phase synthesis of N-cycloguanidinyl-formyl peptides

A novel strategy of solid phase synthesis of N-cycloguanidinyl-formyl peptides has been established and investigated which involved coupling orthogonal protected diaminoacid with resin bound peptide, α-amino group deprotection, guanidinylation of α-amino group by bis-Cbz-1H-pyrazole-1-carboxamidine followed by cleavage and cyclization in solution, and finally removing Cbz by palladium catalyzed hydrogenation. Through this method, cycloguanidine could be introduced to either N-terminus or sidechain of designated peptides. The reaction conditions were facile, straightforward, and totally adaptive to common solid phase peptide synthesis strategy.     

某些新的连位仲、叔二胺的合成

本文用Katritzky,A.R.等人的方法,由苯骈三氮唑、乙二醛、芳香胺或脂肪仲胺的双Mannich缩合产物1,2-二(1-苯骈三氮唑基)-N,N,N',N'-四取代乙二胺和1,7,7-三甲基二环[2,2,1]庚烷-2-基氯化镁反应,生成对称仲、叔连二胺。产率较高。     

Facile synthesis of α,α′ disubstituted N-hydroxypyrrolidines and N-hydroxypiperidines via double 1,4-addition of hydroxylamine

A versatile synthesis of α and α′ disubstituted N-hydroxypiperidine and N-hydroxypyrrolidine by consecutive double 1,4-addition of hydroxylamine on the corresponding bis α,β-unsaturated diester is described. This reaction takes place an environmentally friendly (ethanol/water) system and at room temperature.     

Asymmetric synthesis of C2-symmetric vicinal diamines via reductive dimerization of N-acylpyridinium and related salts

A new route to C2-symmetric diamines via an asymmetric reductive dimerization of 1-acylpyridinium salts and their benzo derivatives is described. This method is practical as the starting heterocycles and chiral auxiliaries are readily available. The titanium reducing agent is inexpensive and easy to prepare. Several novel enantiopure C2-symmetric diamine derivatives were synthesized using this method.     

Facile synthesis of sugar lactols via bromine-mediated oxidation of thioglycosides

Synthesis of a variety of sugar lactols (hemiacetals) has been accomplished in moderate to excellent yields by using bromine-mediated oxidation of thioglycosides. It was found that acetonitrile is the optimal solvent for this oxidation reaction. This approach involving bromine as oxidant is superior to that using N-bromosuccinimide (NBS) which produces byproduct succinimide often difficult to separate from the lactol products.     

Palladium-catalyzed vicinal difunctionalization of internal alkenes: diastereoselective synthesis of diamines

Internal affairs: the first general palladium-catalyzed intermolecular diamination of internal alkenes employs different nitrogen sources, which add to the alkene in a regio- and diastereoselective fashion. The resulting diamination products can be converted directly into a known ligand motif.     

Facile synthesis of ketones from 1,1-disilylethenes via oxidation of gem-disilylalkanes

The oxidation of gem-disilylalkanes, which can be derived from 1,1-disilylethene, alkyllithiums and alkyl halides, affords the corresponding ketones.     

Efficient synthesis of chiral C2-symmetric diamines via allylboration of bis-N,N′-metallodiimines

An enantioselective synthesis of C₂-symmetric bis-homoallylic aromatic and heteroaromatic diamines in 54-89% yields, in 73-94% de and ?98% ee has been achieved via the allylboration of the corresponding N,N′-bis(trimethylsilyl)dialdimines and N,N′-bis(diisobutylalumino)dialdimines with B-allyldiisopinocampheylborane in the presence of methanol, followed by alkaline hydrogen peroxide workup. One-pot synthesis of stable N,N′-bis(benzaldimine-triethylborane) complexes and subsequent allylboration to afford benzene diamines is also described.     

N-Benzylazacyclophane synthesis via aromatic Mannich reaction

A new method for synthesizing phenolic N-benzylazacyclophanes starting from tyramine is presented here. Computational calculations showed that macrocyclization is favored by the formation of hydrogen bond-based templates; these templates are not affected by including benzyl groups in the nitrogen atom of the tyramine moiety. The results showed that N-benzyl groups with electron-donating substituents have more nucleophilic nitrogen atoms, thereby favoring macrocyclization, while electron-withdrawing groups favor polymerization.     

Homocoupling of aldimines mediated by zirconocene: synthesis of vicinal diamines and imidazolidines

The reductive coupling of imines in the presence of the lanthanide-originated zirconocene equivalent allows the synthesis of vicinal diamines or imidazolidines under mild conditions in good yields with high diastereoselectivity.     

Facile direct synthesis of unsymmetrical ureas from N-Alloc-, N-Cbz-, and N-Boc-protected amines using DABAL-Me3

A practical synthetic method for the direct synthesis of unsymmetrically substituted ureas from N-Alloc-, N-Cbz-, and N-Boc-protected amines is described. In this study, efficient direct conversion of the Alloc-, Cbz-, and Boc-carbamate compounds to ureas was achieved in the presence of DABAL-Me₃, an air stable and easily handled reagent. Using this reaction method, both protected aromatic and aliphatic amines were successfully transformed into various trisubstituted and tetrasubstituted ureas with high yields without side product. Our findings offer promising guidelines for direct preparation of useful ureas from N-Alloc-, N-Cbz-, and N-Boc-carbamates.     

Efficient preparation of chiral diamines via Red-Al reduction of N-Boc-protected amino acid-derived secondary amides

Conditions have been developed for the selective reduction of N-Boc-protected amino acid-derived secondary amides, avoiding the formation of overreduction and cyclic urea byproducts. The method is showcased by the efficient formal synthesis of NK-1 antagonist LY303870.     

Synthesis of a series of vicinal diamines with potential biological activity

A broad range of vicinal diamines based on styrene oxide are synthesisedvia mixtures of regioisomeric amino alcohols. The ring opening of the intermediate aziridinium ions by primary amines proceeds with high regioselectivity, leading to the target diamines as single regioisomers for all reaction series. The compounds are of potential biological interest as ligands for cisplatin analogues. Anticancer activity tests of both groups of compounds are in progress.     

Samarium diiodide-induced asymmetric synthesis of optically pure unsymmetrical vicinal diamines by reductive cross-coupling of nitrones with N-tert-butanesulfinyl imines

[reaction: see text] An efficient method for the preparation of optically pure unsymmetrical vicinal diamines by the SmI(2)-induced reductive cross-coupling of nitrones with chiral N-tert-butanesulfinyl imines was developed. This is the first successful example of the highly diastereoselective and enantioselective cross-coupling between two different imine species. It provides a straightforward access to enantiopure unsymmetrical vicinal diamines that are widely applicable in asymmetric synthesis.     

Enantioselective synthesis of vicinal halohydrins via dynamic kinetic resolution

[reaction: see text] Expanding the scope of enantioselective catalysis via DKR, transfer hydrogenation of a variety of cyclic alpha-halo ketones was accomplished using the Noyori/Ikariya (R,R)- or (S,S)-I catalysts and either HCO(2)H/Et(3)N or HCO(2)Na/n-Bu(4)NBr in H(2)O/CH(2)Cl(2) as the hydrogen sources. Good yields of vicinal bromo-, chloro-, and fluorohydrins with excellent de and ee levels were achieved in most cases after a simple tuning of reaction conditions.     

Synthesis of enantiopure vicinal diaminoesters and ketopiperazines from N-sulfinylimidazolidines

A short and efficient synthesis of mono- and bicyclic ketopiperazines bearing methoxycarbonyl substituents is described. The route entails selective protection and solvolysis of N-sulfinylimidazolidines to provide vicinal diaminoesters with the nitrogen atoms suitably differentiated. Then, an N-acylation/cyclization protocol renders the ketopiperazines. In addition a diastereoselective route to an analog of the natural diketopiperazine DKP 593A through a 2-piperidinylglycinate available by this method is described.