Hypochlorous Acid. A Synthesis of α-Chloro-β-Lactones

Herein we report that the reaction of hypochlorous acid with certain α,β-unsaturated acids in a two phase system^1,2 affords α-chloro-β-lactones^3,4 in poor to fair yield. Thus, β-lactones 4, 5, and 6 are obtained from acids 1, 2 and 3, respectively, where the β-carbon of the acid is disubstituted.     

An Efficient Synthesis of α-Bromoacetals via a Combined Chemical and Electrochemical Bromination

α-Bromoacetals (1) are valuable precursors in synthesis of α,β-unsaturated carbonyl compounds (2), 1-alkoxybutadienes² (3), ketene acetals³ (4), 2-methoxyallyl bromides⁴ (5) and other compounds. Because of our interest in the chemistry^5,6 of 3 and 4 we attempted to improve known procedures for the preparation of 1 with the aim to get a short and efficient synthesis of these compounds.     

A Facile Method for the Bishomologation of Ketones to α,β-Unsaturated Aldehydes: Application to the Synthesis of the Cyclohexanoid Components of the Boll Weevil Sex Attractant

The acid-catalyzed isomerization of tertiary vinyl carbinols (2) to the corresponding primary allylic alcohols (5) has been reported numerous times in the chemical literature.¹ In addition, the corresponding acetylenic carbinols (3) have been shown² to rearrange to α,β-unsaturated aldehydes (6) when treated with aqueous acid. Since yields are generally low under the conditions required for the latter transformation, a better method³ involves the isomerization of the corresponding tertiary acetylenic acetate (4) in the presence of silver ion to an allenic acetate, followed by hydrolysis to the desired α,β-unsaturated aldehyde (6).     

Synthesis of Heterobicycles of δ-Lactam Fused with 1,3-Diazaheterocycles by the Reaction of Heterocyclic Ketene Aminals with α,β-Unsaturated Carboxylic Esters

Heterobicycles of δ-lactam fused with imidazolidine (4, 7), hexahydropyrimidine (5, 8), or hexahydro-1, 3-diazepine (6, 9) were synthesized by the reaction of heterocyclic ketene aminals 1, 2 or 3 with ester of α,β-unsaturated carboxylic acids.     

New Synthesis of α-Bromo-α,β-Unsaturated Esters

A synthesis of α-bromo-α,β-unsaturated esters 2 from tert-butyl α-(trimethylsilyl)-α-bromoacetate (1) and carbonyl compounds is described.     

Stereoselective Synthesis of 3-C-Branched-Chain Sugars by Aldol Reaction of Furanos-3-Uloses with Acetone

Abstract

Aldol reaction of 1,2-O-isopropylidene-5-O-tertbutyl-dimethylsilyl-α-D-erythro-pentofuranos-3-ulose (1) with acetone in the presence of aqueous K₂CO₃ afforded 3-C-acetonyl-1,2-O-isopropylidene-5-O-tertbutyl-dimethylsilyl-α-D-ribofuranose(2). Similar reaction of 1,2:5, 6-di-o-isopropylidene- α-D-ribo-hexofuranos-3-ulose (3) afforded 3-C-acetonyl-1,2:5, 6-di-o-isopropylidene- α-D-allofuranose (4) and (1R, 3R, 7R, 8S, 10R)-perhydro-8-hydroxy-5,5,10-trimethyl-2,4,6,11,14-pentaoxatetracyclo[8,3,1,0^1,8,0^3,7] tetradecane. The stereochemistry of the new chiral centers were determined by ¹H NOE experiments.     

Lewis Acid-Mediated Addition of Lithiated Alkyl Phenyl Sulphones and Oxiranes. A Method for Synthesis of α, β-Unsaturated Ketones

Efficiency of the reaction of lithiated alkyl aryl sulphones (1–4) with oxiranes (5, 6) is increased by the presence of BF₃ or CeCl₃. The respective adducts (7–14) were transformed into α,β-unsaturated ketones (15–22) with high yields.     

3-Diethoxyphosphorylpropionic Acid,a Convenient Reagent for the Synthesis of ß,γ-Unsaturated Amides

Abstract

β,γ-Unsaturated amides are versatile intermediates in the organic synthesis e.g. in the synthesis of various analogues of penicillins, cephalosporins, carbapenems, and 1) functionalized monocyclic β-lactam antibiotics. We have now developed a novel route to β,γ-unsaturated. amides 3 starting from di ethoxyphosphory l propionic acid (1). Dilithium derivative of the acid 1 reacts with a variety of carbonyl compounds to give lactons 2. Treatment of 2 with amines results in nucleophilic lacton ring opening with subsequent Horner-Emnons olefination to give 3 (R⁵=HI. Alkylation of the lithiated lacton 2 with alkyl halogens folloved by the ring opening-olefination sequence provides d-substituted α, -unsaturated amides 3 (R⁵=alkyl).     

1,1-DIANIONS OF ALKYL PHENYL SULPHONES AS SYNTHETIC INTERMEDIATES IN CYCLIZATION REACTIONS

Abstract

α-Sulphonyl carbanions are known to be good nucleophiles both in intermolecular and in intramolecular reactions¹. In the same way gem-dimetalloderivatives of alkyl phenyl sulphones I a,b readily add to aldehydes and ketones to give the (β-hydroxy compounds II in the case of dilithioderivatives Ia, while from dimagnesioderivatives Ib α, β-unsaturated sulphones III are also obtained².     

t-Butyldiphenylsilyl-Lithium and Lithium Bis(t-Butyldiphenylsilyl)Cuprate. New Silylating Reagents

t-Butyldiphenylsilyl-lithium reacts with carbonyl derivatives to give α -hydroxysilanes in high yields. Lithium bis (t-butyldiphenylsilyl)cuprate reacts with α, β-unsaturated ketones and esters and with acyl chlorides to give β-silylcarbonyl1 compounds and acylsilanes. β-t-Butyldiphenylsilylketones are masked α, β-unsaturated ketones.     

Reaction of Trialkyl Phosphites with α,β-Unsaturated Carbonyl Compounds

Abstract

Reaction of trialkyl phosphites 1 with α,β-unsaturated oxo-compounds 2 gives oxaphospholenes 3 or/and two types of Arbuzov products, γ-keto-phosphonates 4 and alkyl-enol-ethers 5.     

New Preparation of Cyclic Acyloxyphosphorane by Reaction of Glyoxylic Acid with Phosphorus(III) Compounds

We have recently found that the reaction of α-keto acids (1) with phosphorus (III) compounds (3) yielded cyclic acyloxyphosphoranes(C-AOPs, 4), a new class of pentacovalent phosphorus species having a P-OC(O) group.^{1, 2)} The present paper deals with a new reaction of glyoxylic acid (2) with 3 to give C-AOPs (5) having no substituent at the C-3 position. 1 is an α-keto acid whereas 2 can be taken as an α-formyl acid. Although it is well known in the field of organic chemistry that the formyl group often behaves differently from a keto group, the reaction of 2 with 3 provides an example in which both groups behave in a similar manner.     

N-(Chlorosulfinyl)-Imidazole as a New Imidazole Transfer Reagent1

The usefulness of diimidazoles² such as N, N′-carbonyldi-imidazole (1), and N, N′-thionyldiimidazole (2) in organic synthesis has been accumulated recently. In connection with the continuing our studies on the reaction using 1 or 2 ³ (carbonyl, thionyl, and imidazole transfer reactions), our particular interest was focused on the synthesis of N-(chlorosulfinyl)-imidazole (3) in which one imidazole group in 2 was replaced by the other leaving group (Cl). Also, 3 was interesting for preparative purposes as a chlorine atom could be introduced via the addition reaction of 3 to carbonyl compounds as known in the reaction of 1 or 2 with ketones.     

A General Method for Stepwise Elongation of the (1→5)-α-D-Arabinofuranan Chain

Condensation reaction of 3,5-di-O-benzoyl-1,2-O-(1-cyanoben-zylidene)-β-D-arabinofuranose (2) with benzyl and allyl 2,3-di-O-benzoyl-5-O-triphenylmethyl-α-L-arabinofuranosides (5a and 5b) in methylene chloride in the presence of triphenylcarbenium tetrafluoroborate as catalyst under high vacuum gave α-(1→5)-linked dimeric D-arabinofuranoside derivatives (6a and 6b). One of the dimeric compounds (6a) was debenzoylated, triphenylmethylated, and rebenzoylated to give a dimeric homolog of 5a (8). Similarly for the preparation of 6a, 8 was condensed with 2 to provide an α-(1→5)-linked trimeric D-arabinofuranoside derivative (9). Further elongation of the glycoside chain might be possible in the same way.     

An Allylic Rearrangement Arising from Reaction of Fluoride Ion and A 3-Chloro, 4,5-Unsaturated Uronate Derivative

Reaction of methyl [benzyl 2-[(benzyloxycarbonyl)-amino]-3-chloro-2,3,4-trideoxy-β-L-threo-hex-4-enopyrano-sid]uronate,3,4-trideoxy-β-L-threo-hex-4-enopyranosidjuronate (7) with silver fluoride gave the 5-fluoro, 3,4-unsaturated uronate derivative 8, which, on treatment with methanolic ammonia, afforded the corresponding 5-meth-oxy, uronamide 9. The structures of 8 and 9 were confirmed by spectral data and by x-ray crystallographic analysis of 8. ¹H NMR spectroscopy parameters for 9 and its diastercomen 11 have been used to probe the conformational preferences in solution.     

The Application of the Trichloroacetimidate Method to the Synthesis of α-D-Gluco- and α-D-Galactopyranosides

Abstract

The trichloroacetimidate method has been applied to the construction of α-d-galacto- and α-d-glucopyranosides. The readily available β-trichloroacetimidates of 2,3,4,6-tetra-O-benzyl-d-galacto- and glucopyranose (1-β and 3-β, respectively) have been employed in glycosidations with several monosaccharides (either A, B, C or D) under varying experimental conditions. With the galactose derivative 1-β as a donor and each of the monosaccharides A-D as acceptors, the corresponding disaccharides 1A-1D, were obtained in high yield and with good α-stereoselectivity when employing diethyl ether as solvent and either trimethylsilyl- or tert-butyldimethylsilyl trifluoro-methane sulphonate as catalyst. Glycosidations with the glucose derivative 3-β, as donor, and with the monosaccharide acceptors A, B or D, gave the corresponding disaccharides 3A, 3B and 3D, in high yield but with somewhat lower α-diastereoselectivity than observed with the galactose derivative 1-β. The stereochemical outcome of the reactions is rationalised in terms of possible reaction mechanisms.     

Synthesis of Retro-γ-Ionols and the Corresponding-Ionones1

Both the direct² and the sensitized^3,4 photolyses of (E)-β-ionol (2) have been studied in some detail. In a preliminary publication⁵ we have indicated that direct photolyses of (E)-β-ionol (2) with λ = 254 nm yields (Z)-retro-γ-ionol (3) as the primary product; upon further irradiation 3 is converted into the corresponding (E)-isomer (4) which rapidly yields the bicyclic alcohol 5. A quantitative study revealed that the photoconversion of (E)-β-ionol with λ = 254 nm to 3 is about 10 times faster than the conversion of 3 into (E)-retro-γ-ionol.⁶ This rate difference thus allows the photosynthesis of 3.     

Synthetic Application of Partially Protected Fructopyranoses

Partial deacetonation of 1-O-benzoyl-2,3:4,5-di-O-isopropylidene-β-D-fructopyranose (2) yielded the related 2,3-O-isopropylidene derivative (3) that was subsequently transformed into the corresponding 1-O-benzoyl-4,5-O-dibutylstannylene-2,3-O-isopropylidene-β-D-fructopyranose (4). Reaction of 4 with benzyl bromide proceeded with high regioselectivity to afford 1-O-benzoyl-5-O-benzyl-2/3-O-isopropylidene-β-D-fruc-topyranose (5) together with a small quantity of the 4-O-benzyl derivative (6). Oxidation of 5 gave the 4-oxo derivative (10) which was reduced to yield a mixture of 5 and its 4-epimer (11). Debenzylation of 11, followed by a debenzoylation reaction produced 2,3-O-isopropylidene-β-O-tagatopyranose (13). Aceto-nation of 13 yielded 1,2:3,4-di-O-isopropylidene-α-D-tagatofuranose (14). Structures and configurations of the above compounds were established on the basis of their analytical and spectroscopic data.     

Photochemical Reactions in Carbohydrate Synthesis. Conversion of L-Arabinose Into L-Streptose

Abstract

A synthesis for L-streptose (1) is described. This synthesis differs from those previously reported in several ways, one of which is the use of photochemical reactions in two important steps. These reactions are part of a sequence leading from L-arabinose (2) to 5-deoxy-1,2-O-isopropylidene-β-L-threo-pentofuranos-3-ulose (3). Two other photochemical reactions are considered as a part of the conversion of 3 into L-streptose (1) but neither proved useful. L-Streptose (1) is synthesized from 3 by a sequence of reactions which involves formation of 5-deoxy-l,2-O-isopropylidene-3-C-nitromethyl-β-L-lyxo-furanose (10) and subsequent reaction of 10 with titanium(III) chloride.     

Trans Benzoyl Migration in 1.6-Anhydro-2-azido-4-O-benzoyl-2-deoxy-β-D-glucopyranose in Non-Aqueous Basic Medium

When 1,6-anhydro-2-azido-4-O-benzoyl-2-deoxy-β-D-glucopyranose (¹ (l) was treated with allyl bromide in benzene-tetrahydrofuran solution in the presence of sodium hydride, we obtained the expected reaction product, 3-O-allyl-1,6-anhydro-2-azido-4-O-benzoyl-2-deoxy-β-D-glucopyranose (2), and the rearranged compounds 1,6-anhydro-2-azido-3-O-benzoyl-2-deoxy-β-D-glucopyranose (3) and 4-O-allyl-1,6-anhydro-2-azido-3-O-benzoyl-2-deoxy-β-D-glucopyranose (4).