Intersequence cyclization in copolymers of N-vinyl carbamates

Monomer reactivity ratios determined for the copolymerization of tert-butyl N-vinylcarbamate (r_A = 0.55 ± 0.05) with phenyl N-vinylcarbamate (r_B = 2.08 ± 0.15) indicate that the monomer units are distributed randomly along the polymer chains. The following sequence of reactions was used to cause intersequence cyclization between tert-butyl N-vinylcarbamate and phenyl N-vinylcarbamate units in the copolymers. The extent of cyclization obtained was in accord with that expected for random copolymers.      

300-MHz 1H-NMR spectra of p-cresol-formaldehyde condensates having regular repeating structures

Model p-cresol-formaldehyde condensates having regular sequences of methylene ether and methylene linkages were prepared by the self-condensation of dimethylol derivatives of p-cresol-formaldehyde condensates (2-hydroxy-5-methyl-1,3-benzenedimethanol, 3,3′-methylene-bis[2-hydroxy-5-methylbenzenemethanol] and 3,3′-[(2-hydroxy-5-methyl-m-phenylene)dimethylene]-bis[2-hydroxy-5-methylbenzenemethanol]). 300-MHz ¹H-NMR spectra of these polymers and of their acylated derivatives were recorded and used to develop resonance assignments for the various types of protons present in these polymers. The spectra were found to be sensitive to end-group and sequence distribution effects.     

The proton and carbon-13 NMR spectra of thioxanthone sulfoxide,thioxanthone sulfone and related ylides - chemical shift assignments

The proton and carbon-13 nmr spectra of thioxanthone sulfoxide, thioxanthone sulfone, thioxanthonium bis(carbomethoxyl)methylide and thioxanthonium bis(carbomethoxyl)methylide S-oxide are assigned using 2-D nmr techniques and compared to those of thioxanthone. The pseudo-equatorial methylide fragment shields C4a/5a by ? 11 ppm relative to the corresponding sulfoxide and by ? 4 ppm relative to thioxanthone. The pseudo-axial methylide fragment in the oxysulfonium ylide has the same effect upon C4a/5a as does the pseudo-axial oxygen of the corresponding sulfone. The sulfoxide and the sulfonium ylide have similar chemical shifts for C2/7 (? 131 ppm) as do the sulfone and oxysulfonium ylide (? 133 ppm).     

Organic synthesis with sulphones—XVII: The anti-markownikoff halosulphonylation of olefins via an ionic pathway,and a new method of preparing benzenesulphonyl iodide

Iodine and bromine in the presence of sodium benzenesulphinate react with olefins in acetone solution to give halosulphones resulting from an apparent steric direction of attack at the intermediate halonium ion. A straightforward preparation of benzenesulphonyl iodide from benzenesulphonyl chloride and sodium iodide is also described.     

The direct synthesis of the cyclic sulphamidate of (S)-prolinol: SimultaneousN-protection and activation towards nucleophilic displacement of oxygen.

The preparation of the cyclic sulphamidate of (S)-prolinol has been achieved by reaction with sulphuryl chloride at low temperature. This material has been shown to be susceptible to acid catalysed nucleophilic attack to furnish 2-(NN-dialkylamino)methyl- and 2-(methoxymethy]pyrrolidines after hydrolysis of the intermediate sulphamic acid derivatives.     

An Improved Procedure for Cyclisation of Chalcones to Flavanones Using Celite Supported Potassium Fluoride in Methanol: Total Synthesis of Bavachinin

Chalcones may be cyclised to the corresponding flavanones by stirring with KF-celite suspended in methanol at reflux. This method gives consistently higher conversion than other reported procedures and its utility is illustrated by the synthesis of the linear prenylated flavanone bavachinin.