N-sulfonylimines

Scheme 2.8 Reactions between N-sulfonylimines and allylic ylides.

A large specific microwave effect was observed in the solvent-free synthesis of N-sulfonylimines, a similar type of reaction [64] (Eq. 12). 

The preparation of imines, enamines, nitroalkenes and N-sulfonylimines proceeds via the azeotropic removal of water from the intermediate in reactions that are normally catalyzed by p-toluenesulfonic acid, titanium(IV) chloride, or montmorillonite K 10 clay. A Dean-Stark apparatus is traditionally used which requires a large excess of aromatic hydrocarbons such as benzene or toluene for azeotropic water elimination. 

Expeditious preparation of N-sulfonylimines has been optimized for one-pot solventless operation that involves microwave thermolysis of aldehydes and sulfonamides in presence of relatively benign reagents, calcium carbonate and montmoril-lonite K 10 clay (Scheme 6.23) [76],... 

Use of an alkyl hydrazine as the nucleophile followed the expected course of addition. The resulting product (33), however, opened to an N-sulfonylimine (34) which rearranged to a thia-triazoleoxide (35) in 65% yield (Scheme 7) <86H(24)ii93>. 

When we entered the field, Tomioka et al. had just introduced the dialkylzinc addition to N-sulfonylimines in the presence of chiral amidophosphine-copper(II) complexes, producing high levels of enantioselectivity (up to 94% ee) [27]. At the... 

Diazo(trimethylsilyl)methane reacts with N-sulfonylimines derived from aldehydes to give 2-(trimethylsilyl)aziridines in good yield and with high cis-stereo-... 

Quite recently, there has been significant expansion and development in the alkylation of imines with organozinc reagents using chiral Lewis acid catalysts. In 2000, Tomioka and co-workers reported a copper(II)-chiral amidophos-phine 4-catalyzed asymmetric process for the addition of diethylzinc to N-sul-fonylimines (Scheme 2) [8]. Excellent enantioselectivities (90-94%) and yields (83-99%) were obtained in reactions of N-sulfonylimines derived from arylal-dehydes. 

The chiral phosphine 31 or 32-rhodium complex catalyzed the addition of arystannanes 30 to N-sulfonylimines 29 to give diarylmethylamines 33 with high enantioselectivity (75-96% ee) [21]. The choice of the chiral monoden-tate phosphine ligand is essential for their catalytic asymmetric arylation. With chelating bisphosphine ligands the arylation was very slow. The authors hypoth-... 

Asymmetric aza Morita-Baylis-Hillman reactions of N-sulfonylimines or N-sulfinimines with Michael accepters in the presence a Lewis base catalyst to give the corresponding chiral a-methylene-/ -amino compounds have been described [27]. 

Shi and Xu reported that the chiral amine catalyst 142 also performs quite efficiently in the related addition of N-tosyl aryl imines to methyl vinyl ketone (MVK), to methyl acrylate, and to acrylonitrile (Scheme 6.61) [155]. As shown in Scheme 6.61, enantiomeric excesses > 95% were achieved for several />-N-tosylamino enones 147 obtained by addition of aryl imines (146) to MVK, > 80% for addition to methyl acrylate, and 55% ee (max.) for addition to acrylonitrile (not shown in Scheme 6.61). Reaction times were typically 1-3 days. N-Sulfonylimines derived from aliphatic aldehydes gave rise to complex product mixtures. Under the reaction conditions shown in Scheme 6.61 addition of p-nitrobenzaldehyde to MVK proceeded with only 20% ee. 

He M, Bode JW (2005) Catalytic synthesis of y-lactams via direct annulations of enals and N-sulfonylimines. Qrg Lett 7 3131-3134 He M, Struble JR, Bode JW (2006) Highly enantioselective azadiene Diels-Alder reactions catalyzed by chiral N-heterocyclic carbenes. J Am Chem Soc 128 8418-8420... 

Metal Free Although transition metal catalysts are effective and selective for C—N bond formation via direct C—H bond functionalization, metal-free methodologies are more attractive. Molecular iodine acts as a radical initiator and can be used to direct y-/a-sp3 C—H bond oxidation of sulfonamides in the presence of PhI(OAc)2 (Equation 11.24) [56]. The reaction provides a practical route to pyrrolidines, N-sulfonylimines, and various sulfonamide derivatives. A tentative mechanism is... 

Albrecht and Kresze reported the first examples of [4 + 2] cycloadditions of N-sulfonylimines. Trihalomethylimines 6 and 7, prepared from chloral or fluoral and p-toluenesulfonamide, reacted with 2,3-dimethylbu-tadiene to give cycloadducts in high yields [Eq. (1)]. 

Carboxyl-substituted N-sulfonylimines have also been used in [4 + 2] cycloadditions, and some examples are shown in Scheme 2-11. - Imine 14 adds regioselectively to isoprene to give only one adduct, but diene 15 surprisingly afforder a 3 1 mixture of adducts. The major exo adduct produced from siloxydiene 16 was recently used in total synthesis of the piperidine alkaloids isoprosopinine B and deoxyprosopinine. The highly oxygenated diene 17 was found to react with both acyclic N-sulfonylimine 18 and cyclic imine 19 to afford cycloadducts. 

Acylation reactions with acid chlorides86 also lead to N-substituted products. N-Acyl- and N-sulfonylimines react analogously in nitration reactions (see Section II,A,4). 

Reactions of imines. Silyl alkynyl ethers and aldimines undergo catalyzed condensation, the strained heterocycles that ensue open to afford conjugated amides. YbfOTfjj is also a useful catalyst for the reaction of organocuprates with N-sulfonylimines. ... 

The preparation of imines, enamines, nitroalkenes and N-sulfonylimines proceeds via azeotropic removal of water from the intermediate in reactions that are nor-... 

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