which it acts either as an electron acceptor or an electrophile. Typical examples are those given in the accompanying scheme. Other examples mentioned are Beckmann rearrangements and rearrangements of epoxides into ketones. [Recent Developments in Organic Synthesis in Liquid Sulfur Dioxide. Synthesis 1971,639-645 ; 56 references] [Rd 471 IE -MI
The stereochemistry of cobalt complexes with flexible tetradentate ligands is the subject of a review by G. R. Brubaker, D. P . Schaefer, 3. H . Worrell, and 3. I . Legg. The ligands treated are tetraamines and dithiadiamines with their donor atoms located in a straight chain, and ethylenediamine-N,l diacetate. The preparation of stereoisomers and the determination of their configurations, especially by the measurement of circular dichroism or optical rotatory dispersion, are described in detail. The importance of cobalt complexes of these ligands is due to their comparatively high kinetic stability against substitution reactions ; it is conceivable, therefore, that knowledge gained from the study of cobalt complexes can be used for the determination of configurations of other transition metal complexes which cannot be isolated readily. [Complexes of Cobalt(II1) with Flexible Tetradentate Ligands. Coord. Chem. Rev. 7, 161-195 (1971); 102 references, 8 figures, 10 tables] [Rd 477 IE -HI Substitution and cyclization reactions of suifenyl halides are treated comprehensively in a review by E. Kukle. The main substitution reactions dealt with are the sulfenylations of
BOOK REVIEWS
hydroxy compounds, sulfinic acids, thioles, amines, NH acidic compounds, organophosphorus compounds, Grignard reagents, active methylene-and methine compounds, aromatics, phenols, and N,N-dialkylanilines. Bis(sulfeny1 chlorides) such as (I), a-chlorocarbonylsulfenyl chlorides