Efficacious N-protection of O-aryl sulfamates with 2,4-dimethoxybenzyl groups

Sulfamates are important functional groups in certain areas of current medicinal chemistry and drug development. Alcohols and phenols are generally converted into the corresponding primary sulfamates (ROSO(2)NH(2) and ArOSO(2)NH(2), respectively) by reaction with sulfamoyl chloride (H(2)NSO(2)Cl). The lability of the O-sulfamate group, especially to basic conditions, usually restricts this method to a later stage of a synthesis. To enable a more flexible approach to the synthesis of phenolic O-sulfamates, a protecting group strategy for sulfamates has been developed. Both sulfamate NH protons were replaced with either 4-methoxybenzyl or 2,4-dimethoxybenzyl. These N-protected sulfamates were stable to oxidising and reducing agents, as well as bases and nucleophiles, thus rendering such masked sulfamates suitable for multi-step synthesis. The protected sulfamates were synthesised by microwave heating of 1,1'-sulfonylbis(2-methyl-1H-imidazole) with a substituted phenol to give an aryl 2-methyl-1H-imidazole-1-sulfonate. This imidazole-sulfonate was N-methylated by reaction with trimethyloxonium tetrafluoroborate, which enabled subsequent displacement of 1,2-dimethylimidazole by a dibenzylamine (e.g. bis-2,4-dimethoxybenzylamine). The resulting N-diprotected, ring-substituted phenol O-sulfamates were further manipulated through reactions at the aryl substituent and finally deprotected with trifluoroacetic acid to afford a phenol O-sulfamate. The use of 2,4-dimethoxybenzyl was particularly attractive because deprotection occurred quantitatively within 2 h at room temperature with 10% trifluoroacetic acid in dichloromethane. The four key steps in the protocol described [reaction of 1,1'-sulfonylbis(2-methyl-1H-imidazole) with a phenol, methylation, displacement with a dibenzylamine and deprotection] all proceeded in very high yields.     

Highly efficient nickel/phosphine catalyzed cross-couplings of diarylborinic acids with aryl tosylates and sulfamates

<正>4-Methoxy-4′-methylbiphenyl(3aa) [1] MeO White solid(0.324 g, 82% from aryl tosylate, 0.356 g, 90% from aryl sulfamate); m.p. 111–112 °C; 1H NMR(400 MHz,CDCl3) δ 7.50(d, J = 8.4 Hz, 2H), 7.44(d, J = 8.0 Hz, 2H), 7.21(d, J = 8.0 Hz, 2H), 6.95(d, J = 8.8 Hz, 2H), 3.82(s, 3H), 2.37(s, 3H); 13 C NMR(100 MHz, CDCl3) δ 159.0, 138.0, 136.4, 133.8, 129.5, 128.0, 126.6, 114.2, 55.4, 21.1. 4,4′-Dimethylbiphenyl(3ab) [1] White solid(0.320 g, 88% from aryl tosylate, 0.346 g, 95% from aryl sulfamate); m.p. 122–123 °C; 1H NMR(400 MHz,CDCl3) δ 7.47(d, J = 8.0 Hz, 4H), 7.22(d, J = 8.0 Hz, 4H), 2.37(s, 6H); 13 C NMR(100 MHz, CDCl3) δ 138.4, 136.8, 129.5, 126.9, 21.2.     

Effects of temperature on nitration of sulfamates

Ammonium dinitramide (ADN) has attracted great interest as a potential oxidizer for next generation rocket propellants. It is a halogen-free alternative to ammonium perchlorate, which is currently in wide used as a solid propellant oxidizer. However, in ADN synthesis, N-nitration is necessary to form the N-(NO₂)₂ group. Using a reaction calorimeter, the thermal behavior of nitration of sulfamates (K, Na, and NH₄) using a mixture of acids (HNO₃/H₂SO₄ and HNO₃/AcOH) as the nitration agent was examined. The heat of decomposition of potassium sulfamate at ?10 °C was greater than that at 20 °C. The heat of decomposition decreased in the following order: K salt>Na salt>NH₄ salt in HNO₃/H₂SO₄. The dipole moments of the sulfamates were calculated, and the results revealed that the electronic states of nitrogen were different. Thus, the dipole moments of sulfamates affect the decomposition heat of sulfamates. The heat of decomposition in HNO₃/AcOH was larger than that in HNO₃/H₂SO₄.     

Solid-phase parallel synthesis of 17alpha-substituted estradiol sulfamate and phenol libraries using the multidetachable sulfamate linker

We report an application of the multidetachable sulfamate linker in the synthesis of two model libraries of N-derivatized 17alpha-piperazinomethyl estradiols (phenols and sulfamates) by solid-phase parallel chemistry. The solid-phase precursor, a 3-sulfamoyl-17alpha-(N-trifluoroacetyl-piperazinomethyl) estradiol, was synthesized in solution from estrone and loaded efficiently onto trityl chloride resin as polymeric support. After cleavage of the trifluoroacetyl protecting group, sequential acylation reactions with five Fmoc-protected amino acids and five carboxylic acids were performed to introduce two levels of molecular diversity. Finally, the resins were split into two parts, and acidic (5% trifluoroacetic acid in dichloromethane) and nucleophilic (piperazine in tetrahydrofuran) cleavages were used to generate libraries A (5 x 5 sulfamates) and B (5 x 5 phenols) members in overall yields of 18-66% and high HPLC purities (87-96%) without purification steps. A preliminary screening test for inhibition of steroid sulfatase showed that the phenols were clearly weaker inhibitors, as compared to their sulfamate analogues. The most potent inhibitors were those with suitable hydrophobic amino acid and carboxylic acid substituents. Thus, compounds with a phenylalanine residue as the first element of diversity inhibited over 90% of steroid sulfatase activity at a concentration of 1 nM in homogenates of HEK-293 transfected cells, being as potent as the leading inhibitor 17alpha-tert-butylbenzyl estradiol 3-O-sulfamate previously reported. These results suggest that the steroid sulfatase inhibitory potency of estradiol derivatives, sulfamoylated or not, can be increased by the hydrophobic effect of a suitable substituent introduced in the proximity of the D ring of the steroid. The present work also demonstrated the efficiency and the cleavage versatility of the sulfamate linker to generate libraries of compounds with relevant biological importance, phenols and sulfamates.     

Rapid nickel-catalyzed Suzuki-Miyaura cross-couplings of aryl carbamates and sulfamates utilizing microwave heating

High-speed and scalable nickel-catalyzed cross-coupling of arylboronic acids with aryl carbamates and sulfamates is achieved by using sealed-vessel microwave processing.     

Nickel catalyzed cross-coupling of aryl C-O based electrophiles with aryl neopentylglycolboronates

The efficiency of mesylates, sulfamates, esters, carbonates, carbamates, and methyl ethers as C-O-based electrophiles attached to the 1- or 2-position of naphthalene and to activated and nonactivated phenyl substrates was compared for the first time in Ni-catalyzed cross-coupling with phenyl neopentylglycolboronates containing electron-rich and electron-deficient substituents in their para-position. These experiments were performed in the presence of four different Ni(II)- and Ni(0)-based catalysts. Ni(II)-based catalysts mediate the cross-coupling of most 2-naphthyl C-O electrophiles with both arylboronic acids and with neopentylglycolboronates when K(3)PO(4) is used as base. The same catalysts are not efficient when CsF is used as base. However, Ni(0)-based catalysts exhibit selective efficiency, and when reactive, their efficiency is higher than that of Ni(II)-based catalysts in the presence of both K(3)PO(4) and CsF. These results provide both reaction conditions for the cross-coupling, and for the elaboration of orthogonal cross-coupling methodologies of various C-O based electrophiles with aryl neopentylglycolboronates. With the exception of mesylates and sulfamates the efficiency of all other 2-naphthyl C-O electrophiles was lower in cross-coupling with aryl neopentylglycolboronates than with arylboronic acids.     

Synthesis and nitration of condensation products of sulfamates with aliphatic amines and formaldehyde

A method for the synthesis of 5-alkyl-1,3-dinitro-1,3,5-triazacyclohexanes and linear polynitramines was proposed. It includes the reaction of aliphatic amines with sulfamates and formaldehyde and nitration of the reaction products. The yield and composition of nitramino derivatives depend on the conditions of the condensation and nitration. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1088–1091, June, 2000.     

Efficient synthesis of N-oxysulfonyl formamidines through thionyl chloride-promoted reaction of sulfamates with formamides

N-Oxysulfonyl formamidine derivatives have been efficiently synthesized under mild conditions through direct condensation of various sulfamates and formamides in the presence of thionyl chloride. The scope of this reaction was investigated, and a plausible mechanism was proposed. The resulting N-oxysulfonyl formamidines can be converted to sulfamates through appropriate deprotection.     

Enantioselective Rhodium‐Catalyzed Coupling of Arylboronic Acids, 1,3‐Enynes,and Imines by Alkenyl‐to‐Allyl 1,4‐Rhodium(I) Migration

A chiral rhodium complex catalyzes the highly enantioselective coupling of arylboronic acids, 1,3‐enynes, and imines to give homoallylic sulfamates. The key step is the generation of allylrhodium(I) species by alkenyl‐to‐allyl 1,4‐rhodium(I) migration.     

有机硼酸类催化剂在有机合成中的应用

综述了有机硼酸类作为催化剂应用于有机合成反应中的最新研究进展, 重点介绍了所发现的各种有机硼酸催化剂在缩合反应、羧酸还原反应、Diels-Alder反应中的催化活性以及反应机理. 硼酸催化剂因具有催化效率高、反应条件温和、可重复使用等优点, 必将在有机合成催化领域中得到更广泛的应用.     

Enantioselective Rhodium‐Catalyzed Coupling of Arylboronic Acids, 1,3‐Enynes,and Imines by Alkenyl‐to‐Allyl 1,4‐Rhodium(I) Migration

A chiral rhodium complex catalyzes the highly enantioselective coupling of arylboronic acids, 1,3‐enynes, and imines to give homoallylic sulfamates. The key step is the generation of allylrhodium(I) species by alkenyl‐to‐allyl 1,4‐rhodium(I) migration.     

Ni(COD)2/PCy3 catalyzed cross-coupling of aryl and heteroaryl neopentylglycolboronates with aryl and heteroaryl mesylates and sulfamates in THF at room temperature

Reaction conditions for the Ni(COD)(2)/PCy(3) catalyzed cross-coupling of aryl neopentylglycolboronates with aryl mesylates were developed. By using optimized reaction conditions, Ni(COD)(2)/PCy(3) was shown to be a versatile catalyst for the cross-coupling of a diversity of aryl neopentylglycolboronates with aryl and heteroaryl mesylates and sulfamates containing both electron-donating and electron-withdrawing substituents in their para, ortho, and meta positions in THF at room temperature. This Ni-catalyzed cross-coupling of aryl neopentylglycolboronates is also effective for the synthesis of heterobiaryls and biaryls containing electrophilic functionalities sensitive to organolithium and organomagnesium derivatives. In combination with the recently developed Ni-catalyzed neopentylglycolborylation, all Ni-catalyzed routes to functional biaryls and heterobiaryls are now easily accessible.     

Diastereoselectively Switchable Asymmetric Haloaminocyclization for the Synthesis of Cyclic Sulfamates

An asymmetric synthesis of cyclic sulfamates by catalytic haloaminocyclization of primary sulfamate ester derivatives is described. The remarkable reversal of diastereoselectivity was found to be dependent on the halogen source and the chiral catalyst. By using privileged complexes of N,N′‐dioxides with Sc(OTf)₃ or Lu(OTf)₃ as the catalyst, a variety of enantioenriched syn‐ and anti‐cyclic sulfamates or related trans‐aziridines could be obtained in 92–99 % ee and up to 97 % yield.     

钯催化的酰胺羰基化反应

酰胺羰基化的发现为氨基酸及其衍生物的合成提供了一个新方法。该合成方法 步骤简洁，只需一步即可从醛、酰胺-氧化碳合成N-酰基氨基酸，而且该反应是原 子经济型反应。与钴催化的酰胺羰基化相比，钯催化的反应条件更为温和，催化效 率也大为提高，对基团有更广普的适应性。简述近所来这一领域的新进展。     

Synthesis of mono- and bis(aminomethyl)dioxanes fromN-[3-(2-chloroethoxy)-2-hydroxypropyl]sulfamates

N-Substituted aminomethyl- and 2,5-bis(aminomethyl)-1,4-dioxanes were prepared by cyclization of the corresponding potassiumN-[3-(2-chloroethoxy)-2-hydroxypropyl]sulfamates under the action of an alkaline agent followed by alcoholysis of the resulting sulfamic acids.     

Exploring new uses for C-H amination: Ni-catalyzed cross-coupling of cyclic sulfamates

[reaction: see text] Benzene-fused cyclic sulfamates are prepared from ortho-substituted phenolic starting materials through selective C-H amination or olefin aziridination. These unique heterocycles will engage in Ni-catalyzed cross-coupling reactions with aryl- and alkyl-Grignard reagents. Application of modern tools for C-N and C-C bond formation thus makes readily available functional amine derivatives and augments the possible uses for C-H amination in synthesis.     

A novel synthesis of bis-(α-hydroxyalkyl)phosphinic acids involving microwave irradiation

A simple, efficient, and general method has been developed for the synthesis of bis-(α-hydroxyalkyl)phosphinic acids from hypophosphorous acid using microwave irradiation. Bis-(α-hydroxyalkyl)phosphinic acids were obtained in high yield under mild conditions by reaction of hypophosphorous acid with aldehydes under microwave irradiation.     

The reaction of sulfamic acid derivatives with epoxides

A new method for obtaining N-(b-hydroxyalkyl)sulfamates with 50–95 % yields by the reaction of sulfamic acid derivatives with epoxides is proposed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1146–1147, June, 1993.     

Catalyst and solvent-free amidation of inactive esters of N-protected amino acids

A catalyst free procedure for the preparation of amides from inactive esters of N-protected amino acids and various amines is demonstrated under mild reaction conditions. Our effort to recover excess amine and generated alcohol is an approach towards environment friendly and cost effective synthesis under easy operational conditions.     

Synthesis of C-9 oxidised N-acetylneuraminic acid derivatives as biological probes

Sialic acids are 9-carbon acidic sugars involved in a number of important biological processes and human diseases. As part of our ongoing interest in the development of novel sialic acids as biological probes, we have developed an efficient and simple synthesis of C-9 oxidised sialic acid derivatives. The key oxidative step involves the use of TEMPO under carefully controlled aqueous pH conditions.