Navigation

0 Hits

  • Previous / Next

You are using Science Of Synthesis as a Guest.
Please login to access the full content or check if you have access via
22.7.2.2 Ortho Esters and Halogenated Derivatives (Update 2024)

DOI: 10.1055/sos-SD-122-00258

Zhu, H.; Fan, Q.Science of Synthesis Knowledge Updatesearly view.

General Introduction

This chapter provides a comprehensive supplement to the previous Science of Synthesis contribution on the preparation of ortho esters and halogenated derivatives (Section 22.7.2).[‌1‌] The first part focuses on the synthesis of 1,1-dihalogenated ethers and 1-halogenated acetals (Section 22.7.2.2.1). Protocols to 1,1-dihalogenated ethers mainly contain conversions of aliphatic formates, reactions through difluorocarbene precursors and the dichloromethyl radical, and difluoromethylations mediated by silver(I) fluoride and xenon difluoride (Sections 22.7.2.2.1.122.7.2.2.1.5). Dihalomethyl ethers have always been synthesized via difluorocarbene intermediates (Sections 22.7.2.2.1.2.122.7.2.2.1.2.6) and the dichloromethyl radical (Section 22.7.2.2.1.3). In recent years, various difluoromethylation reagents have been developed as effective replacements for chlorodifluoromethane, such as difluoromethyl trifluoromethanesulfonate, (bromodifluoromethyl)trimethylsilane, fluoroform, diethyl (bromodifluoromethyl)phosphonate, chlorodifluoromethyl phenyl ketone, and chlorodifluoromethyl phenyl sulfone. These reagents can react with substrates to afford difluoromethyl ethers under mild conditions with good substrate compatibility. Few examples have been reported about approaches to 1-halogenated acetals (Sections 22.7.2.2.1.622.7.2.2.1.8). Although direct fluorinations have always been alternative approaches, functional-group compatibilities are the key issues in most reactions. Desulfurative fluorination reactions are also widely used, involving hydrogen fluoride and bromine trifluoride. In addition, reactions using phosphorous pentachloride and chlorine–fluorine exchange reactions can give high yields of α,α-dihalogenated acetals.

Mee eeeeee eeee ee eeee eeeeee (Meeeeeee 88.8.8.8.8.888.8.8.8.8.88) eeeeee eee eeeeee eeeeeee eee eeeee eeeee eeeeeeeee, eeeeeeeee eeeeeeeeeeeeeee eeeeeeeeeeeeeee, eeeeeeeeeeee eeeeeeeeeeee eeeeeeeee, eeeeeeeeeee, eeeeeeeeee-eeeee-eeeeeeeee MM eeeeeeeeeeeeeeeee, [8 + 8] eeeeeeeeee, eeeeee eeeeeeeeeee, eeeeeeeeeeeeee, eee eeeeeeee ee eeeeee eeeeee.

References


Cookie-Einstellungen