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Highly effective indium(III)-catalyzed reductive bromination or iodination of a variety of carboxylic acids with 1,1,3,3-tetramethyldisiloxane (TMDS) and a source of bromine or iodine is described. This functional group interconversion has high tolerance for several functional groups, such as halogens, a hydroxy group, a nitro group, an olefin part, and a sulfide moiety. This indium catalytic system is also applicable to the reductive iodination of aldehyded, acyl chlorides, and esters. Furthermore, this reducing system can be applied to the one-pot synthesis of alkyl halides and amine derivatives via the addition of nucleophiles. Insight into the reaction mechanism was gained via the time course of 1H and 13C NMR monitoring experiments and the corresponding stepwise reactions.

The reducing system is selective for carboxylic acids and other functional groups are not attacked.

A variety of carboxylic acids is converted to primary alcohols applying InBr3 as a catalyst and tetramethyldisoxane as a reducing agent [cf.

The title nucleosides (16U, C, G and H) were synthesized from pyrimidine and purine ribonucleosides in about 30% overall yield in 6 steps via key intermediates, protected 3′-deoxy-‘arabino’-nucleosides, which were obtained by deoxygenative [1,2]-hydride shift and β-elimination reactions of sulfonylated ribo-counterparts. Xanthine analogues (9X and 16X) were prepared from the corresponding guanine nucleosides. The unprotected 3′-deoxy-‘arabino’-nucleosides (9U,C,A,G,H,X) and their azido nucleosides 16 did not show any significant activity against either HIV in vitro or P388 leukaemia in mice.

The enantioselective hydrolysis of (±)-4-(1-acetoxyethyl)-N-(cyclohexylcarbamoyl)-benzenesulfonamides 3 with lipase Amano P from Pseudomonas sp. in a water-saturated solvent gave (R)-4-(1-hydroxyethyl)-N-(cyclohyxylcarbamoyl)benzenesulfonamide 2 (39%, >99% ee) and unchanged (S)-3 (50%, 62% ee). On the other hand, enantioselective esterification of (±)-2 with lipase Amino P in the presence of vinyl acetate provided (R)-3 (41%, >99% ee) and unchanged (S)-2 (46%, 78% ee).

A substoichiometric amount (10-20 mol%) of dibutyltin dichloride 1 was found to be effective for promoting the regioselective 2'-O-tosylation of adenosine 2 with TsCl in a one-pot manner, wherein a turnover step for tin dichloride 1 was involved. Dibutylchlorotin hydroxide 7, dibutyltin oxide 8, bis(dibutylchlorotin) oxide 10, its hydroxy congener 12, and tributyltin chloride 14 were also effective in a substoichiometric amount for the 2'-O-tosylation of the nucleoside 2. The method was applicable to some methyl glycopyranosides. The tosylation with tin dichloride 1 was not sensitive to the presence of water in the reaction mixture. Possible reaction pathways are discussed.

Various secondary amines were smoothly oxidized to the corresponding imines at −78 °C by using N-tert-butylphenylsulfinimidoyl chloride and DBU.

Various linear and non-linear primary amines were oxidatively deaminated to afford the corresponding carbonyl compounds in good to excellent yields by the following procedure: (i) initial formation of their N-cyclohexylated or N-mesylated derivatives, (ii) subsequent oxidation of these derivatives by using N-tert-butylphenylsulfinimidoyl chloride (1) and DBU, (iii) one-pot acid-hydrolysis of thus formed imines to carbonyl compounds.

Polymer-supported sulfinimidoyl chloride was prepared in four steps from chloromethyl polystyrene resin. Stoichiometric and catalytic oxidations of various alcohols to the corresponding carbonyl compounds were carried out cleanly by using the prepared polymer-bound oxidant.

1,1-Disubstituted and trisubstituted alkenes were converted into the corresponding β,γ-unsaturated amines 4 via three steps: the initial formation of α,β-unsaturated diphenylsulfonium triflates 2 from alkenes and diphenyl(trifluoromethanesulfonyloxy)sulfonium trifluoromethanesulfonate (1), followed by double bond migration of 2 to β,γ-unsaturated sulfonium triflates 3 with primary or secondary amines, and successive nucleophilic substitution of 3 with these amines.

Two polymer-supported sulfinimidoyl chlorides, i.e., 4-(N-tert-butylchlorosulfinimidoyl)phenoxymethylpolystyrene (3) and 4-(N-tert-butylchlorosulfinimidoyl)polystyrene (10), were prepared from chloromethylpolystyrene and polystyrene, respectively. Stoichiometric or catalytic oxidation of various primary and secondary alcohols using these polymer-supported sulfinimidoyl chlorides proceeded smoothly, and the corresponding aldehydes and ketones were conveniently prepared in good-to-high yields by simple work-up procedures. The polymer-supported oxidant 10 was recycled repeatedly by chlorination of a used polymer 11 with N-chlorosuccinimide (NCS) after stoichiometric oxidation.

Primary and secondary alcohols were smoothly oxidized to the corresponding aldehydes and ketones in high yields at room temperature with 1.1 equiv. of molecular bromine by using a catalytic amount of N-t-butyl-2-nitrobenzenesulfenamide in the coexistence of potassium carbonate and molecular sieves 4A.

2′-Azido-2′,3′-dideoxyadenosine ( 9 ) has been synthesized from adenosine ( 1 ) in 6–8 steps. The key intermediate, N 6 , O 5′ -bis(4,4′-dimethoxytrityl)-9-(3-deoxy-β- d - threo -pentofuranosyl)adenine ( 6a ), was prepared in a one-flask manner by two methods, (a) in 95% yield by a deoxygenative [1,2]-hydride shift of a 3′- O -mesyl-adenosine derivative ( 5e ) and subsequent reduction of an in situ -generated 2′-keto derivative ( 10 ) with mixed reagents, Mg(OMe) 2 -NaBH 4 ; (b) by elimination of N 6 , O 5′ -bis(4,4′-dimethoxytrityl)-3′- O -mesyl-2′- O -tosyl- and -2′,3′-di- O -tosyladenosines ( 5b and 5c ) to form an enol tosylate ( 11 ), which was converted into 6a in good yield. In these reactions, KOH could be used in place of Mg(OMe) 2 . 2′-Detosylation of 5b occurred to some extent (∼30%) prior to the β-elimination. The overall yields of 9 from 1 were 4 and 36% by the use of the first and second procedures, respectively. Similarly, 3′-azido-2′,3′-dideoxyadenosine ( 17 ) was synthesized from 1 in 17% overall yield via the known 9-(2-deoxy-5- O -trityl-β- d - threo -pentofuranosyl)adenine ( 13 ), which was prepared by the deoxygenative reduction of 2′- O -tosyl-5′- O -trityladenosine ( 12 ) with LiEt 3 BH.

The reaction of appropriately protected 2′-O-tosyladenosines with methylmagnesium bromide (or iodide) gave 9-(2-deoxy-3-C-methyl-β-D-threo-pentofuranosyl)adenine after deprotection. The same reaction on 3′-O-tosyladenosine derivatives afforded an epimeric pair of 2′-C-methyl-3′-deoxy sugar nucleosides. The modified structures of the sugar moieties were determined unambiguously.

Practical syntheses of 3′-deoxy-β-D-threo-pentofuranosyl-uracil, -cytosine, -adenine, and -guanine (3U, C, A, G) from the corresponding ribonucleosides by two one-pot reactions with readily accessible reagents are described. The key reactions are the selective 3′-O-methanesulphonylations of the ribonucleosides, the deoxygenative [1,2]-hydride shift of the methanesulphonates, and the reduction of in situ generated 3′-deoxy-2′-keto nucleosides therefrom.