Mechanistic and Computational Studies of Exocyclic Stereocontrol in the Synthesis of Bryostatin-like Cis-2,6-Disubstituted 4-Alkylidenetetrahydropyrans by Prins Cyclization

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• 作者：Yasuyuki Ogawa ; Phillip P. Painter ; Dean J. Tantillo ; Paul A. Wender
• 刊名：The Journal of Organic Chemistry
• 出版年：2013
• 出版时间：January 4, 2013
• 年：2013
• 卷：78
• 期：1
• 页码：104-115
• 全文大小：637K
• 年卷期：v.78,no.1(January 4, 2013)
• ISSN：1520-6904

文摘

The Prins cyclization of syn-尾-hydroxy allylsilanes and aldehydes gives cis-2,6-disubstituted 4-alkylidenetetrahydropyrans as sole products in excellent yields regardless of the aldehyde (R鈥? or syn-尾-hydroxy allylsilane substituent (R鈥? used. By reversing the R鈥?and R鈥?groups, complementary exocyclic stereocontrol can be achieved. When the anti-尾-hydroxy allylsilanes are used, the Prins cyclization gives predominantly cis-2,6-disubstituted 4-alkylidenetetrahydropyrans, now with the opposite olefin geometry in excellent yield. The proposed reaction mechanism and the observed stereoselectivity for these processes are supported by DFT calculations.