The aggregation in dilute aqueous solutions of several ω-substituted single-chain quaternary ammonium surfactants has been studied by Krafft temperature and critical aggregation/micelle concentration measurements and by cryo-transmission electron microscopy:  (16-carboxyhexadecyl)trimethylammonium bromide (1a); (16-methoxycarbonylhexadecyl)trimethylammonium bromide (1b); (17,18-dihydroxyoctadecyl)trimethylammonium bromide (1c). Octadecyltrimethylammonium bromide (2) was included for comparison. The aggregation of 1a was also studied by Raman spectroscopy. Surfactant 1a at pH 6.8 forms ribbonlike fibers with lengths of up to 1.2 μm and cross sections of 3−4 nm × 12−16 nm; at pH 2.2, ribbon to rodlike fibers; and at pH 11.5, wormlike aggregates. Surfactants 1b and 1c at pH 6.8 form rod-shaped aggregates. The Raman spectroscopy results indicated that 1a is not in a fully extended conformation within its fibers at pH 6.8. Tentative structural models have been proposed for the aggregates of surfactants 1.

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Route selection, process development and large-scale preparation of selectively benzoylated and fluorinated d-glucopyranoses, required as glycosyl donors for the synthesis of the SGLT inhibitor SAR7226, are discussed.

The utility of 1,5,7-triazabicyclo[4.4.0]dec-5-ene as a reagent to facilitate efficient amide formation by reaction of an amine with an unactivated ester was demonstrated on pilot-plant scale as a key step in the synthesis of an H-PGDS inhibitor.

The photo-rearrangement of mixtures of azoxybenzene 4 and, successively, [15~,15N']4, [180]4, and [2-14C]4 were carried out. Kinetic isotope effects (KIE) were calculated from measurements of isotopic ratios in both recovered 4 and the product, 2-hydroxyazobenzene (6). Analogous rearrangement of mixtures of 2,2'-azoxynaphthalene (8) Introduction In recent years sporadic attempts have been made to detect intermediates in photochemical reactions in solution by measuring heavy-atom (other than hydrogen isotopes) kinetic isotope effects (KIE). The basis for this approach was expressed by Schutte and Havinga in 1967, who used the photo-Fries rearrangement to try to answer "the question that has been raised whether photochemical reactions after electron excitation pass through a transition state of appreciable energy of activation" (1). Schutte and Havinga used 4-metho~~phenyl-['~~]acetate for measuring the carbon KIE in the photorearrangement of the ester into 2-acetyl-4-methoxyphenol, and found that within experimental error the rearrangement did not exhibit an isotope effect. They concluded, therefore, that rearrangement began in the electronically excited state (singlet) and proceeded very rapidly through vibrationally excited states in a process that required no thermal energy of activation.The quest was later pursued by Kwart and co-workers (2), who sought evidence for a vibrationally excited ground state intermediate in the photochemical rearrangement of the ylide 1 into the diazepine 3. In this case an inverse carbon KIE was found with the use of specifically labeled [13c]1, and the result was attributed to the formation of the intermediate 2 in the pathway from excited 1 to product (3) (reaction [I]). To our knowledge this is the first time in which a heavy-atom KIE has been found in a photochemical rearrangement.