Hot water-promoted cyclopropylcarbinyl rearrangement facilitates construction of homoallylic alcohols

Abstract

In refluxing 9 : 1 (v/v) H2O-1,4-dioxane and without an additional catalyst, the rearrangements of various types of cyclopropyl carbinols were attempted. It was found that the reactions generally gave homoallylic alcohols in good to very high chemical yields. Rearrangements of bicyclic or tricyclic cyclopropyl carbinols readily gave the desired ring-expanded cyclic homoallylic alcohols which are difficult to synthesize by other means.

Sarglaromatics A–E: A Class of Naphthalene-Like Architecture Fused Norlindenane Sesquiterpene Dimers from Sarcandra glabra

“…The hydroxyl group of 3 at the allyl position was easily dehydrated, and aromatic cyclization gave compounds 1 and 2 with a naphthalene ring system. In this process, carbocation intermediate V could also open the ring of cyclopropane under the attack of EtO – and then isomerize to produce 4 . − The electron-rich methyl group (Me-13′) in path B forms a double bond with C-11 to terminate the free-radical reaction ( IV′ ), and 5 is produced through a pathway similar to 3 .…”

Nucleophilic Substitution at Quaternary Carbon Stereocenters

“…Mechanistically related, the S N 1′ and S N 2′ reactions have also been extensively explored when a double bond is used as a relay for nucleophilic substitution . As the chemical reactivity of a cyclopropane ring closely resembles a CC double bond, the analogy of vinylog nucleophilic substitution has been reported for the acid-catalyzed homoallylic rearrangement of cyclopropyl carbinols (Scheme b) en route to trans olefins. , Later, Honda has investigated the selectivity of this type of homoallylic rearrangement by using substituted cyclopropylsilyl methanols . The diastereoselective 1,6-addition reaction promoting selective ring fragmentation (equivalent to a S N 2″) of alkenylcyclopropyl methanol derivatives was recently achieved by amphiphilic organoalane nucleophiles (Scheme c) .…”

Metal-Free Synthesis of Oxazinones and Their Reductive Ring Opening to Provide Cyclopropyl Carbinols

“…In total synthesis, both taxol 25 and the epothilones 26,27 have been prepared via cyclopropyl carbinol intermediates. While the utility of these compounds is evident, previous methods to generate them have revolved primarily around the addition of hydride or organometallic reagents to acylcyclopropanes 95 (Scheme 11, A), [28][29][30][31][32][33][34][35][36][37][38][39] and the addition of organometallic cyclopropyl species of the general structure 97 to carbonyl compounds 98 (Scheme 11, B). [40][41][42][43][44] The primary problem with these syntheses is the electrophilic cyclopropyl moiety and its propensity to undergo ring opening reactions (Scheme 12), thus limiting the substrate scope.…”