@article {2107, title = {Synthetic studies toward halichlorine: Complex azaspirocycle formation with use of an NBS-promoted semipinacol reaction}, journal = {Journal of Organic Chemistry}, volume = {73}, number = {11}, year = {2008}, note = {ISI Document Delivery No.: 307MRTimes Cited: 13Cited Reference Count: 90Hurley, Paul B. Dake, Gregory R.}, month = {Jun}, pages = {4131-4138}, type = {Article}, abstract = {The investigations of a synthetic route incorporating a NIBS-promoted semipinacol rearrangement to the 6-azaspiro[4.5]decane fragment within halichlorine (1) are presented. A convergent approach was pursued, utilizing two chiral, enantiomerically enriched building blocks, 2-trimethylstannyl piperidene 10 and substituted cyclobutanone 19. Noteworthy synthetic operations in this study include the following: (a) a highly diastereoselective NBS-promoted semipinacol reaction that established four stereogenic centers in ketone 25 and (b) the use of a N-p-toluenesulfonyl-2-iodo-2-piperidene as a precursor to a basic organometallic reagent, which was critical to the success of the coupling of fragments 10 and 19.}, keywords = {(+/-)-PINNAIC ACID, ASYMMETRIC-SYNTHESIS, BAEYER-VILLIGER OXIDATION, CARBOXYLIC-ACIDS, CRIEGEE REARRANGEMENT, ETHYLMAGNESIUM BROMIDE, ORGANIC-SYNTHESIS, PINNAIC ACID, RING-CLOSING METATHESIS, SPIROCYCLIC CORE}, isbn = {0022-3263}, url = {://000256323500018}, author = {Hurley, P. B. and Dake, G. R.} } @article {829, title = {Investigations of alpha-siloxy-epoxide ring expansions forming 1-azaspirocyclic ketones}, journal = {Journal of Organic Chemistry}, volume = {69}, number = {17}, year = {2004}, note = {ISI Document Delivery No.: 845XHTimes Cited: 13Cited Reference Count: 97}, month = {Aug}, pages = {5676-5683}, type = {Article}, abstract = {The construction of 1-azaspirocyclic cycloalkanones using a siloxy-epoxide semipinacol ring expansion process was examined. Functionalized 1-azaspiro[5.5]undecan-7-ones (1-azaspirocyclic cyclohexanones) proceeded in high chemical yields with complete diastereoselectivity using titanium tetrachloride as the Lewis acid promoter. The formation of functionalized 6-azaspiro[5.4]-decan-1-ones (1-azaspirocyclic cyclopentanones) proceeded in high chemical yield with little diastereoselectivity. Modification of reaction parameters such as the Lewis acid promoter or the nature of the silyl ether allowed for the preferential formation of either ("anti" or "syn" 1,2 alkyl shift) diastereomeric product. An explanation for the different reactivity profiles between the cyclobutanol silyl ethers and cyclopentanol silyl ethers is provided.}, keywords = {1ST TOTAL-SYNTHESIS, ALDOL ALDOL PROCESS, ASYMMETRIC-SYNTHESIS, BAEYER-VILLIGER OXIDATION, LEWIS-ACIDS, ORGANIC-SYNTHESIS, PRACTICAL, QUATERNARY CARBON CENTERS, REARRANGEMENT, SEMI-PINACOL, SILYL ETHER REARRANGEMENTS, STEREOSELECTIVE CONSTRUCTION}, isbn = {0022-3263}, url = {://000223278200021}, author = {Dake, G. R. and Fenster, M. D. B. and Fleury, M. and Patrick, B. O.} }