And ring closing reactions

In 1970 ring-opening and ring-closing reactions of 2,2-dialkyl-1,3,2-dioxa- and -1,3,2-oxathia-stannolanes with carbon disulfide and phenyl isothiocyanate involving nucleophilic attack at the tin atom were discovered <70CC235>. Since these reactions are described as proceeding via a cyclic transition state they will be considered in Section 4.24.2,5.10. 

Scheme 4. One-pot synthesis of a carbazole via consecutive Buchwald-Hartwig amination and ring-closing reactions ...

Dimethyl carbonate, (MeO) jCO, is a recognized substitute for phosgene in many carbonylatlon and ring-closing reactions [595]. For example [595] ... 

ACYCLIC DIYNE METATHESIS CONDENSATION, ADIMET, AND RING CLOSING REACTIONS OF DIYNES... 

The substitution inertness of Cr(III) and the lability of Cr(II) have allowed Hecht et al. to observe some ring-opening and ring-closing reactions of amino-carboxylate ligands. The experiments used a stationary Hg drop electrode in 1.0 M NajSO at pH 8.5, apparently at ambient temperature. Their observations can be explained by Scheme 10.2, where the aliphatic substituent R gives the trans-N,N geometry shown. 

Interestingly, the solution of 54 can then be cooled and reirradiated, and the elec-trocyclic ring-opening and ring-closing reactions can be repeated many times. 

Electrocyclic ring opening and ring closing reactions of alternating polyenes are controlled by orbital symmetry. 

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