Regioselectivity Influences in Platinum-Catalyzed Intramolecular Alkyne O–H and N–H Additions
作者:Jeff P. Costello、Eric M. Ferreira
DOI:10.1021/acs.orglett.9b03557
日期:2019.12.20
The steric and electronic drivers of regioselectivity in platinum-catalyzed intramolecular hydroalkoxylation are elucidated. A branch point is found that divides the process between 5-exo and 6-endo selective processes, and enol ethers can be accessed in good yields for both oxygen heterocycles. The main influence arises from an electronic effect, where the alkyne substituent induces a polarization
The preparation of (α-alkylidene)tetrahydrofurans by tungsten catalyzed decarboxylation of aldol precursors
作者:Tomoya Tanzawa、Jeffrey Schwartz
DOI:10.1016/s0040-4039(00)61775-6
日期:1992.11
A series of substituted (alpha-alkylidene)tetrahydrofurans was prepared by tungsten catalyzed reaction of substituted hydroxyfuroic acids. These reactions likely involve beta-lactone intermediates which decarboxylate under the reaction conditions, and rates for olefin synthesis correlated with donor properties of substituents at C(4).
Catalytic and metal-free intramolecular hydroalkoxylation of alkynes
作者:Alexandre Jean、Jacques Rouden、Jacques Maddaluno、Michaël De Paolis、Jérôme Blanchet
DOI:10.1016/j.tetlet.2019.01.020
日期:2019.2
Benzyltrimethylammonium hydroxide act as an efficient metal-free catalyst for the intramolecular hydroalkoxylation of alkynes. Notably, the use of microwave irradiation allowed reaction to operate in only two minutes. Under optimized reaction conditions, linear alkynes bearing aryl and heteroaryl substituents were successfully cyclized with good level of stereoselectivity. (C) 2019 Elsevier Ltd. All rights reserved.