Diagnostic OH ¹H‐NMR shift differences in syn and anti ß‐Hydroxy Ethers

Abstract

In a pair of diastereomeric ß‐hydroxy ethers the relative 1H‐NMR chemical shift of the OH proton is diagnostic for the syn or anti stereostructure. This is probably based on the presence of internally hydrogen‐bonded structures. The rule is therefore restricted to those compounds for which only this type of internal hydrogen bonding is accessible.

Synthesis of Chiral α,δ-Dioxygenated Allylic Stannanes as Reagents for Carbohydrate Synthesis and Homologation

“…In all cases, this proton was deshielded in the syn isomer in comparison to the anti as a consequence of more effective internal hydrogen bonding. A similar trend was previously noted by Landmann and Hoffmann 1 Chairlike transition states leading to syn and anti -1,2-diol derivatives. 1 Chemical Shift Comparisons for the OH Proton of Adductsδ OH R 1 R 2 R 3 adduct syn anti OTBS TBS ( E )-MeCHCH 5.1b 2.55 2.22 OTBS TBS ( E )-TBSOCH 2 CHCH 5.1c 2.56 2.21 OTBS TBS n -C 6 H 13 C⋮C 5.1d 2.55 2.29 OTBS TBS TBSOCH 2 C⋮C 5.1e 2.37 2.13 OTBS MOM c -C 6 H 11 5.2a 2.37 2.09 OTBS MOM ( E )-MeCHCH 5.2b 2.67 2.40 OTBS MOM ( E )-TBSOCH 2 CHCH 5.2c 2.67 2.42 H TBS n -C 6 H 13 6.3a 2.39 2.35 H TBS c -C 6 H 11 6.3b 2.70 2.57 H TBS n -C 6 H 13 C⋮C 6.3e 2.55 2.33 H MOM ( E )-MeCHCH 6.4c 2.53 2.23 H MOM ( E )-TBSOCH 2 CHCH 6.4d 2.58 2.29 …”

The Configurational Stability of an Enantioenrichedα-Thiobenzyllithium Derivative and the Stereochemical Course of Its Electrophilic Substitution Reactions; Synthesis of Enantiomerically Pure, Tertiary Benzylic Thiols[1,2]

“…The relative configurations of the aldehyde adducts were deduced from 1 H NMR and 13 C NMR spectroscopic data. Apart from accepted empirical rules concerning the chemical shifts of the OH group ( 1 H NMR25) and the benzylic methyl group (1‐CH 3 , 13 C NMR26) some additional proof was collected as shown in Table 3. Whereas the 1 H NMR criteria for 1‐CH 3 27, 28 and 2‐H28 coincide with results from investigations of the appropriate O ‐benzylcarbamates, the 13 C NMR regularity concerning C‐2 was firstly found for the series of thiocarbamates ent ‐ 11 h / h′ – ent ‐ 11 l / l′ .…”

An NMR Method for Assigning Relative Stereochemistry to β-Hydroxy Ketones Deriving from Aldol Reactions of Methyl Ketones

“…NMR methods have been used extensively for these purposes, based on the recognition that the viscinal 1 H− 1 H constants for protons on adjacent stereogenic centers typically fall in the range J anti > J syn . However, the J analysis is not necessarily straightforward for molecules with three or more contiguous stereocenters (owing to the need to minimize gauche pentane interactions), molecules with vicinal heteroatom substituents that prefer to adopt gauche relationships, , and molecules with functional groups that can participate in hydrogen-bonding networks …”