R. David Crouch

Selective Deprotection of Silyl-Protected Phenols Using Solid NaOH and a Phase Transfer Catalyst

Aryl silyl ethers can be deprotected to yield phenols in good to excellent yields using a biphasic system of 10 equivalents of NaOH and catalytic Bu4NHSO4 in 1,4- dioxane. Alkyl silyl ethers prepared using a variety of silyl protecting groups survive under these conditions, allowing selective deprotection of silyl-protected phenols in the presence of silyl-protected alcohols.

Deprotection of silyl ethers using ZnBr2 and H2O in CH2Cl2

Abstract TES- and TBS-protected alcohols undergo deprotection upon treatment with excess ZnBr2 and water in CH2Cl2 at 44–50°C. TIPS-protected alcohols also undergo deprotection but at slower rates. TBDPS-protected alcohols and silyl-protected phenols are unreactive under these conditions, allowing for selective deprotection of differentially-protected bis-silyl ethers.

Recent Advances in Silyl Protection of Alcohols

Abstract Silyl protection/deprotection of alcohols continues to play an important role in organic synthesis. New silyl groups and methods for their introduction and removal are constantly being developed and offer chemists a wider range of options in their use. In recent years, though, silyl protecting groups have been given expanded roles beyond their traditional use of temporarily rendering alcohols inactive. Merging the silyl protection/deprotection of alcohols with such modern methodologies as asymmetric techniques, fluorous chemistry, and nanoscience has added additional value to these temporary components of synthetic intermediates. This review covers developments in the use of silyl protecting groups of alcohols reported in the period 2007 to the end of 2011. GRAPHICAL ABSTRACT

The Pechmann reaction

A solid acid-catalyzed version of the Pechmann reaction for the synthesis of coumarins is described. The Pechmann reaction is a multiple-transformation process which is not a part of the normal organic chemistry curriculum. However, each transformation (hydroxyalkylation, transesterification, dehydration) is one that can be understood by students, and by applying the known mechanisms in sequence, the correct product can be predicted.

A mild, convenient, non-acidic conversion of enol ethers into alcohols using Hg(OAc)2NaBH4

Abstract Alkyl enol ethers can be converted into the corresponding alcohols in good to excellent yields by treatment with aqueous Hg(OAc) 2 NaBH 4 in one reaction flask. This method is sufficiently mild to allow the survival of acid-sensitive groups such as silyl ethers, THP-protected alcohols and N -Boc-protected amines.

Rapid, Acid‐Mediated Deprotection of Silyl Ethers Using Microwave Heating

Abstract Microwave heating of triethylsilyl (TES)‐ and tert‐butyldimethylsilyl (TBS)‐protected 1° and 2° alcohols in a mixture of equal parts acetic acid, tetrahydrofuran (THF), and water allows deprotection in as little as 5 min. tert‐butyldiphenylsilyl (TBDPS)‐ and triisopropylsilyl (TIPS)‐protected alcohols and silyl‐protected phenols are stable in these conditions. Thus, selective deprotection of TES‐ and TBS‐protected alcohols in the presence of TIPS or TBDPS ethers is possible. Similarly, alkyl silyl ethers can be deprotected in the presence of aryl silyl ethers.

Microwave-Accelerated Suzuki-Miyaura Coupling Reactions Using Potassium Aryltrifluoroborates

The microwave-accelerated Suzuki-Miyaura coupling of bromoarenes and potassium aryltrifluoroborates in good to excellent yields is described. The method does not require the use of phosphine ligands or phase-transfer catalysts and reactions are complete in 20 minutes.

Molecular Diversity and Combinatorial Chemistry: Principles and Applications (Tetrahedron Organic Chemistry Series) (Pirrung, Michael C.)

This monograph stems from a series of lectures and courses on combinatorial chemistry that the author has taught at Caltech, Duke, and the University of California–Irvine. The intent of the book is to provide an introduction to the vast and growing field of combinatorial chemistry.

PHOTOMETRIC DETERMINATION OF THE RATE EXPRESSION FOR MNO4- MEDIATED ORGANIC OXIDATIONS

Photometric procedure for studying the kinetics of the MnO4- mediated oxidation of mandelic acid in KOH.