A mild and efficient oxidation of alcohols with o-iodoxybenzoic acid (IBX) catalyzed by beta-cyclodextrin in a water/acetone mixture (86:14) has been developed. A series of alcohols were oxidized at room temperature in excellent yields.
A wide variety of epoxides and aziridines were converted to the corresponding b-azido alcohols and b-azido amines with sodium azide using Oxone ® in aqueous acetonitrile. The reactions were highly regioselective and efficient with excellent yields at room temperature under mild reaction conditions. Epoxides 2 and aziridines 3 are among the most useful synthetic intermediates in organic synthesis. Due to their three membered ring strain, they undergo facile, regioand stereoselective ring-opening reactions with various nucleophiles, yielding a broad range of valuable products. 4,5 Among these, the azidolysis of epoxides and aziridines enjoys a prominent position for the preparation of azido alcohols 6 and azido amines, 7 respectively. The vicinal azido alcohols are precursors of amino alcohols 8 which are well known as b-blockers and a common structural components in a vast group of natural products. 9 Further, they have also been utilized in carbohydrate chemistry 10 or in the chemistry of nucleosides. 11 The azido amines obtained upon ring opening are easily transformed to valuable vicinal diamines. 12 The classical reagents for azidohydrin synthesis are the combined use of TMSN 3 or NaN 3 and a Lewis acid or a transition metal complex. 13 In most of epoxide ring-opening reactions with NaN 3 under either alkaline or acidic conditions, suffer from high temperatures or long reaction times. In addition to these, side reactions, isomerizations, epimerization and rearrangements have also observed by the alkaline conditions of the reaction. It has been found that NaN 3 impregnated on a calcium cation exchange Y-type Zeolite induces the nucleophilic ring opening of epoxides in protic solvents affording azidohydrins. 14 Other reported reagents are tributyltinazide and dibutyltinazide, in DMF. 15 Use of phase transfer catalyst 16 has also been reported recently for the preparation of azidohydrins. Even though several procedures have appeared for the ring opening of epoxides, a limited number of methods have been available for the ring-opening reactions of aziridines. The most straightforward route to azido amines involves the regioselective ring opening of aziridines with TMSN 3 in the presence of a promoter. Tetrabutylammonium fluoride was found to promote the ring-opening reaction of aziridines with TMSN 3 . 12 Yeung and co-workers 17 reported the chromium complex mediated ring-opening reaction of aziridines with TMSN 3 . Transition metal-based complexes 18 were also used when N-benzoylaziridines were the substrates, but the rearrangement to oxazolines took place. As part of a programme aimed at the synthesis of epoxides and aziridines and their applications in organic synthesis, we have studied the ring opening reactions of these small heterocyclic compounds. 19 We recently found that potassium peroxymonosulfate, commonly sold as Oxone ® (2 KHSO 5 , KHSO 4 , K 2 SO 4 ) catalyze in an extraordinarily effective way the alcoholysis 20 of epoxides and aziridines in aqueous methanol. On this basis, we looked for an analog...
Aromatic acetals have been deprotected to the corresponding aldehydes under biomimetic conditions for the first time using beta-cyclodextrin in water under neutral conditions, thereby overcoming many of the drawbacks associated with earlier methodologies. This method, apart from being simple with regard to recycling of the catalyst, also has the potential for industrial applications.
Ketone N,N-dimethylhydrazones are rapidly and chemoselectively deprotected to the corresponding ketones in high yields by CeCl 3 •7H 2 O supported on silica gel under microwave irradiation. The method is compatible with acid sensitive substrates.
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