Sulfonyl chlorides, amino functionalization using

The most important group of derivatives for the amino function (Fig. 7-4) is the carbamate group, which can be formed by reactions with acids, acid chlorides or acid anhydrides. A series of chlorides as 2-chloroisovalerylchloride [1], chrysanthe-moylchloride [2] and especially chloride compounds of terpene derivatives (cam-phanic acid chloride [3], camphor-10-sulfonyl chloride [4]) are used. The a-methoxy-a-trifluoromethylphenylacetic acid or the corresponding acid chloride introduced by Mosher in the 1970s are very useful reagents for the derivatization of amines and alcohols [5]. 

Excess Acid. The helpful function of excess sulfuric acid as an inexpensive, low-viscosity solvent for most sulfonic acids is often overlooked because of the difficulty of recovering a product dissolved in it, or because of the disposal problem often encountered. Sulfonation of most of the hydroxyl, amino, nitro, and carboxylic derivatives of benzene, naphthalene, and anthraquinone is facilitated in this manner by the presence of excess acid. The same effect applies to anthraquinone itself, to petroleum lubricant fractions during sulfonation to mahogany and green acids, and to the sulfation of fatty oils. Chlorosulfonic acid, used in large excess for the conversion of aromatic compounds to sulfonyl chlorides by chlorosulfona-tion, functions in a similar manner. 

Significant counterion effects are observed in the enantioselectivity of addition of diethylzinc to benzaldehyde using a titanium/a-acetyl-(5 )-BINOL system. rran5-l,2-Diaminocyclohexane - a common motif used in asymmetric catalysis - exhibits a dihedral angle of ca 60° between the amino groups, whereas rranx-ll,12-diamino-9,10-dihydro-9,10-ethanoanthracene (124) is constrained to >110°. Further functionality and chirality has been incorporated by the formation of bis-sulfonamides of (124), using (S j-camphor sulfonyl chloride. The... 

An intramolecular allyl silane/N-sulfonyl iminium ion cyclization has also been used as a pivotal step in an approach to the tricyclic core of the unique marine alkaloid sarain A [46]. The starting material was aziridine ester 129 (Scheme 25) which was elaborated to amide 130. An important step in the synthetic strategy was thermolysis of 130 to an azomethine ylide, which underwent stereospecific intramolecular 1,3-dipolar cycloaddition with the Z-alkene to produce bicyclic lactam 131 [47]. This compound was then elaborated into allyl silane 132. It was then possible to replace the lactam N-benzyl functionality with a tosyl moiety, leading to 133, and subsequent reduction of the carbonyl group afforded the desired cyclization precursor a-hydroxy sulfonamide 134. Exposure of 134 to ferric chloride promoted cyclization to a single stereoisomeric tricyclic amino alkene 136 having the requisite sarain A nucleus. It is believed that the intermediate N-sulfonyl iminium ion cyclizes via the conformation shown in 135. 

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